Primary Fibromyalgia

The cause of fibromyalgia is not known. Some patients associate trauma and infections with the development of symptoms, but there is no hard evidence in favour of such triggering events. However, many factors are known to aggravate the existing symptoms. Cold, damp weather, mental disturbance, physical or mental stress, and also physical inactivity have all been associated with fibromyalgia (Wolfe 1986).

A major feature is patients waking up in the morning feeling tired. Abnormal serotonin metabolism is associated with both the sleep disturbance and decreased pain threshold typical in these patients (Goldberg 1987).

The symptoms of fibromyalgia start insidiously with persisting widespread musculoskeletal pains, multiple general symptoms such as fatigue, stiffness, subjective swelling of the fingers not observed by the examining physician, non-refreshing sleep and muscular pain after exertion. About one-third of the patients have additional symptoms, such as irritable bowel syndrome, tension headaches, premenstrual syndrome, numbness and tingling in the extremities, dryness of mouth and eyes and constriction of the blood vessels in the fingers when exposed to cold (Raynaud’s phenomenon).

Typically, a patient with fibromyalgia has a large variety of symptoms, which, with the exception of tender points, have no objective counterparts. Fibromyalgia runs a chronic course. Most of the patients continue to have symptoms with varying intensity. Complete remission is an exception. In primary fibromyalgia, no laboratory signs referring to inflammatory arthritis are present. Patients with inflammatory arthritis (e.g. rheumatoid arthritis) can also have fibromyalgic symptoms, in which case the term secondary fibromyalgia is applied.

There is no one test for fibromyalgia. The diagnosis of fibro- myalgia is based on the history of the patient and on the clinical observation of tender points (figure 1). The prevalence of fibro-myalgia in the general population is 0.5 to 1%. Most (75 to 90%) of the patients are women, usually between 25 and 45 years of age; children are rarely affected.

Figure 1. Tender point sites in fibromyalgia.

The American College of Rheumatology has set criteria for the classification of fibromyalgia (figure 2).

Figure 2. The American College of Rheumatology 1990 criteria for the diagnosis of fibromyalgia.

Diagnosis

Other ailments with similar symptoms must be excluded. Widespread pain must be present for at least three months. In addition there must be pain in 11 of the 18 tender point sites shown in figure 1 when pressed by an examiner’s finger.

Rheumatoid Arthritis

About 1% of the adult population has rheumatoid arthritis. The onset of the disease is usually at 30 to 50 years of age, with females having a threefold higher risk than males. The prevalence of the disease increases in older populations.

The cause of rheumatoid arthritis is not known. It is not inherited, but genetic factors increase the risk for the development of the disease. In addition to one or multiple genetic factors, some environmental triggering factors are thought to play a role in its pathogenesis, and viral or bacterial infections are heavily suspected.

Rheumatoid arthritis usually starts gradually. Typically, the patient has mild swelling of the small joints of fingers, and tenderness of the feet that manifests in a symmetrical fashion. If joints on one hand, for example, are involved it is likely that the same joints on the other hand will be affected. Stiffness of hands and feet in the morning is a major symptom. The patient often has fatigue and can have mild fever. Laboratory features include evidence of inflammation (elevated erythrocyte sedimentation rate and C-reactive protein level) and often mild anaemia. About 70% of the patients have circulating rheumatoid factor (autoantibody against IgG-class immunoglobulin). In early cases, radiological examination of hands and feet is often normal, but later on, most patients develop radiological evidence of joint destruction (erosions). The diagnosis of rheumatoid arthritis is based on a mixture of clinical, laboratory and radiological findings (see figure 3).

Figure 3. Criteris for the diagnosis of rheumatoid arthritis.

The diseases which most often cause differential diagnostic problems are degenerative joint diseases of the hands, arthritis following infections, spondylarthropathies, and some rare connective tissue diseases (Guidelines 1992).

Patient education to diminish the work-load of the joints, use of ergonomic appliances, good footwear, and proper treatment of infections form the basis of preventive measures. Treatment guidelines are given in table 1.

Table 1. Guidelines for the treatment of rheumatoid arthritis

Spondylarthropathies

Epidemiology and aetiology

Spondylarthropathies include typical clinical entities such as ankylosing spondylitis and some forms of arthritides associated with psoriasis, with chronic inflammatory bowel diseases, or with bacterial infections in the urogenital tract or in the gut (so called reactive arthritis). The diseases are common. The prevalence of the most chronic form, ankylosing spondylitis, in Western populations varies between 0.1 and 1.8% (Gran and Husby 1993). Three new cases of transient arthritis such as reactive arthritis compared to one patient with ankylosing spondylitis are estimated to occur annually in a population of 10,000. Most of the patients who develop spondylarthropathy are young adults, between 20 and 40 years of age. There is evidence that the mean onset of symptoms for patients with ankylosing spondylitis is increasing (Calin et al. 1988).

Spondylarthropathies have a strong genetic component since a majority of the patients have an inherited genetic marker, HLA-B27. The frequency of this marker is about 7 to 15% in Western populations; 90 to 100% of patients with ankylosing spondylitis and 70 to 90% of patients with reactive arthritis are HLA-B27 positive. However, at population levels, most of the subjects with this marker are healthy. Therefore, it is thought that exogenous factors, in addition to the genetic susceptibility, are needed for the development of the disease. Such triggering factors include bacterial infections in the urogenital tract or in the gut (table 2) skin lesions, and chronic inflammatory bowel diseases. The evidence in favour of infections is most direct in the case of reactive arthritis. Salmonella infections are widely increasing, as a sequel of which an increase in the cases with joint complications can be expected. Agriculture and poultry can be the sources of these infections. As to yersinia infections, pigs harbour yersinia bacteria in their tonsils. Slaughtering followed by storage of the meat products in the cold has been suggested to contribute to the dispersion of infections in humans. In patients with ankylosing spondylitis, however, usually no preceding infections can be traced as an initiating event. Recent results have, however, focused on the finding that patients with ankylosing spondylitis often have asymptomatic chronic gut inflammation, which could serve as a triggering factor or as a contributing inflammatory focus in the chronicity of the disease.

Table 2. Infections known to trigger reactive arthritis

Signs and symptoms

Peripheral arthritis is asymmetric, affects large joints, and has a predilection to low extremities. The patients often also have inflammatory low back pain, worse by night and relieved by movement, not by rest. A typical feature is a tendency to inflammation of the junction between tendons and bones (enthesopathy), which can manifest itself as pain under the heel or in calcaneus at the insertion of Achilles tendon. In addition to inflammation in the joints and at ligamentous insertions, patients also can have inflammatory symptoms in eyes (iritis or conjunctivitis), skin (psoriasis, skin lesions in palms, soles, or leg induration) and sometimes in the heart.

The following are the diagnostic criteria for spondylarthro- pathy (Dougados et al. 1991).

Inflammatory low back pain

or

Joint inflammation (synovitis):

• asymmetric
• predilection to low extremities

and

at least one of the following:

• positive family history for spondylarthropathy
• psoriasis
• inflammatory bowel disease
• buttock pain changing from side to side
• pain at the junction between tendon and bone (enthesopathy).

Patients with ankylosing spondylitis have low-back pain, worse by night, and tenderness between the spine and the pelvis at the sacroiliac joints. They can have limited mobility of the spine with chest tenderness. A third of the patients have peripheral arthritis and enthesopathy. The cornerstone of the diagnosis of ankylosing spondylitis is the presence of radiological changes in the sacroiliac joints; there is a loss of space between the joints, and bony outgrowths. Such changes add to the diagnostic accuracy of patients with spondylarthropathy but are necessary only in the case of ankylosing spondylitis.

Gout

Epidemiology and aetiology

Gout is a metabolic disorder that is the most common cause of inflammatory arthritis in men. Its prevalence among adults varies from 0.2 to 0.3 per 1000, and is 1.5% in adult males. The prevalence of gout increases with age and with increasing serum urate levels.

Hyperuricemia (high level of uric acid in serum) is a risk factor. Contributing factors are chronic kidney diseases which lead to renal insufficiency, hypertension, use of diuretic drugs, high alcohol intake, lead exposure and obesity. Gouty attacks are precipitated by hypersaturation of joint fluid with uric acid; the precipitated crystals irritate the joint, with the development of acute arthritis.

Signs and symptoms

The natural course of gout runs through several stages from a- symptomatic hyperuricemia to acute gouty arthritis, asymptomatic periods, and to chronic tophaceous gout (gout with nodules).

Acute gouty arthritis often manifests itself as an acute inflammation in one joint, usually at the base of the big toe. The joint is very tender, swollen and highly painful; it is often red. The acute attack can subside spontaneously within days. If untreated, repeated attacks can occur, and in some patients these continue (during the subsequent years) so that the patient develops chronic arthritis. In these patients, urate deposits can be observed in the ear helices, at the elbows, or at the Achilles tendons, where they form non-tender subcutaneous palpable masses (tophi).

Infectious Arthritis

Epidemiology and aetiology

In children, infectious arthritis often develops in a previously healthy child, but adults often have some predisposing factor, such as diabetes, chronic arthritis, use of glucocorticosteroid or immunosuppressive therapy, previous injections or trauma in the joint. Patients with endoprosthesis are also susceptible to infections in the operated joint.

Bacteria are most often the cause of infectious arthritis. In immunosuppressed patients, fungi can be found. Although bacterial infection in the joint is rare, it is very important to recognize, because, if untreated, the infection rapidly destroys the joint. The microbes can reach the joint by circulation (septic infection), by direct penetrating wound or during a joint injection, or from an adjacent infectious focus.

Signs and symptoms

In a typical case, a patient has acute joint inflammation, usually in one single joint, which is painful, hot, red and tender to movement. There are general symptoms of infection (fever, chills) and laboratory evidence of acute inflammation. The joint aspiration is turbid, and in microscopic examination a high number of white blood cells are seen, with positive stain and cultures for bacteria. The patient can have signs of a focus of infection elsewhere, such as pneumonia.

Osteoporosis

Epidemiology and aetiology

Bone mass increases from childhood until adolescence. Women gain 15% less bone density than men. It is at its highest between 20 and 40 years, after which there is a constant decrease. Osteoporosis is a condition in which bone mass decreases and bones become susceptible to fracture. Osteoporosis is a major cause of morbidity in the elderly. The most important manifestation is lumbar and hip fractures. About 40% of women who have reached 70 years have suffered from fractures.

Peak bone mass is influenced by genetic factors. In women, bone mass decreases after menopause. The decrease of bone mass in men is less distinct than in women. In addition to lack of oestrogen, other factors influence the rate of bone loss and the development of osteoporosis. These include physical inactivity, low amount of calcium in the diet, smoking, coffee consumption and low body weight. Use of systemic corticosteroid therapy is also associated with enhanced risk for osteoporosis.

Signs and symptoms

Osteoporosis can be asymptomatic. On the other hand, the most distinct manifestation of osteoporosis is bone fracture, typically that of the hip, vertebrae (spine) and wrist. Hip and wrist fractures usually are a result of falling, but vertebral fractures can develop insidiously after a trivial trauma. The patient has back pain, kyphosis and loss of height.

Bone Cancer

Epidemiology and aetiology

Primary malignant bone tumours are uncommon. They occur most often in children and young adults. Osteosarcoma is the most frequent of the malignant bone tumours. It is most frequently observed in the second decade of life, and in older adults it can result secondary to a bone disease (Paget’s disease). Ewing’s sarcoma is also mostly observed in children, who present with destructive changes in the pelvis or in the long bones. Malignant tumours originating from the cartilage (chondrosarcoma) can occur in many cartilage areas. In adults, malignant bone lesions are often metastatic (i.e., the primary malignant disease is somewhere else in the body).

Most malignant primary tumours have no known aetiology. However, Paget’s disease of bone, osteomyelitis, osteonecrosis and radiation injury have been associated with malignant transformation. Bone metastases are frequent in primary cancers of the breast, lung, prostate, kidney or thyroid gland.

Signs and symptoms

Pain, limitation of movement and swelling are present in patients with osteosarcoma. In addition to bone pain, patients with Ewing’s sarcoma often have systemic symptoms such as fever, malaise and chills. Chondrosarcomas can cause varying symptoms depending on the site of the tumour and its histologic details.

Osteomyelitis

Epidemiology and aetiology

Osteomyelitis is a bone infection that is usually bacterial, but can be fungal or viral. In an otherwise healthy person, osteomyelitis is a rare event, but in patients with chronic diseases such as diabetes or rheumatoid arthritis, infection in the body can spread by the bloodstream or by direct invasion to bones. In children, the most favoured site for the spreading is the shaft of long bone, but in adults the infection is often in the spine. A focal point from which an infection can spread by bloodstream or by direct invasion, penetrating or blunt trauma, prior orthopaedic surgery (insertion of prosthesis) can all be complicated by osteomyelitis.

Signs and symptoms

Acute bone infection of the long bones is associated with fever, chills and bone pain. Spinal osteomyelitis can cause more vague symptoms with progressive pain and low-grade fever. Infections around a prosthesis cause pain and tenderness when moving the operated joint.

Back

Human beings possess an extraordinary capacity to adapt to their environment and to their immediate surroundings. Of all the types of energy that humans can utilize, light is the most important. Light is a key element in our capacity to see, and it is necessary to appreciate the form, the colour and the perspective of the objects that surround us in our daily lives. Most of the information we obtain through our senses we obtain through sight—close to 80%. Very often, and because we are so used to having it available, we take it for granted. We should not fail to keep in mind, however, that aspects of human welfare, like our state of mind or our level of fatigue, are affected by illumination and the colour of the things that surround us. From the point of view of safety at work, visual capacity and visual comfort are extraordinarily important. This is because many accidents are due to, among other reasons, illumination deficiencies or errors made by the worker because he or she finds it hard to identify objects or the risks associated with machinery, conveyances, dangerous containers and so on.

Visual disorders associated with deficiencies in the illumination system are common in the workplace. Due to the ability of sight to adapt to situations with deficient lighting, these aspects are sometimes not considered as seriously as they should be.

The correct design of an illumination system should offer the optimal conditions for visual comfort. For the attainment of this goal an early line of collaboration between architects, lighting designers and those responsible for hygiene at the worksite should be established. This collaboration should precede the beginning of the project, to avoid errors that would be difficult to correct once the project is completed. Among the most important aspects that should be kept in mind are the type of lamp that will be used and the lighting system that will be installed, the distribution of luminance, illumination efficiencies and the spectral composition of light.

The fact that light and colour affect the productivity and the psycho-physiological well-being of the worker should encourage the initiatives of illumination technicians, physiologists and ergonomists, to study and determine the most favourable conditions of light and colour at each work station. The combination of illumination, the contrast of luminances, the colour of light, the reproduction of colour or the selection of colours are the elements that determine colour climate and visual comfort.

Factors that Determine Visual Comfort

The prerequisites that an illumination system must fulfil in order to provide the conditions necessary for visual comfort are the following:

• uniform illumination
• optimal luminance
• no glare
• adequate contrast conditions
• correct colours
• absence of stroboscopic effect or intermittent light.

It is important to consider light in the workplace not only by quantitative criteria, but also by qualitative criteria. The first step is to study the work station, the precision required of the tasks performed, the amount of work, the mobility of the worker and so on. Light should include components both of diffuse and of direct radiation. The result of the combination will produce shadows of greater or lesser intensity that will allow the worker to perceive the form and position of objects at the work station. Annoying reflections, which make it harder to perceive details, should be eliminated, as well as excessive glare or deep shadows.

The periodic maintenance of the lighting installation is very important. The goal is to prevent the ageing of lamps and the accumulation of dust on the luminaries that will result in a constant loss of light. For this reason it is important to select lamps and systems that are easy to maintain. An incandescent light bulb maintains its efficiency until the moments before failure, but this is not the case with fluorescent tubes, which may lower their output down to 75% after a thousand hours of use.

Levels of illumination

Each activity requires a specific level of illumination in the area where the activity takes place. In general, the higher the difficulty for visual perception, the higher the average level of illumination should be as well. Guidelines for minimal levels of illumination associated with different tasks exist in various publications. Concretely, those listed in figure 1 have been gleaned from European norms CENTC 169, and are based more on experience than on scientific knowledge.

Figure 1. Levels of illumination as a function of tasks performed

The level of illumination is measured with a luxometer that converts luminous energy into an electrical signal, which is then amplified and offers an easy reading on a calibrated scale of lux. When selecting a certain level of illumination for a particular work station the following points should be studied:

• the nature of the work
• reflectance of the object and of the immediate surroundings
• differences with natural light and the need for daytime illumination
• the worker’s age.

Units and magnitudes of illumination

Several magnitudes are commonly used in the field of illumination. The basic ones are:

Luminous flux: Luminous energy emitted per unit of time by a light source. Unit: lumen (lm).

Luminous intensity: Luminous flux emitted in a given direction by a light that is not equally distributed. Unit: candela (cd).

Level of illumination: Level of illumination of a surface of one square metre when it receives a luminous flux of one lumen. Unit: lux = lm/m².

Luminance or photometric brilliance: Is defined for a surface in a particular direction, and is the relation between luminous intensity and the surface seen by an observer situated in the same direction (apparent surface). Unit: cd/m².

Contrast: Difference in luminance between an object and its surroundings or between different parts of an object.

Reflectance: Proportion of light that is reflected by a surface. It is a non-dimensional quantity. Its value ranges between 0 and 1.

Factors that affect the visibility of objects

The degree of safety with which a task is executed depends, in large part, on the quality of illumination and on visual capacities. The visibility of an object can be altered in many ways. One of the most important is the contrast of luminances due to reflection factors, to shadows, or to colours of the object itself, and to the reflection factors of colour. What the eye really perceives are the differences of luminance between an object and its surroundings, or between different parts of the same object. Table 1 lists the contrasts between colours in descending order.

The luminance of an object, of its surroundings, and of the work area influence the ease with which an object is seen. It is therefore of key importance that the area where the visual task is performed, and its surroundings, be carefully analysed.

Table 1. Colour contrasts

The size of the object that must be observed, which may be adequate or not depending on the distance and the angle of vision of the observer, is another factor. These last two factors determine the arrangement of the work station, classifying different zones according to their ease of vision. We can establish five zones in the work area (see figure 2).

Figure 2. Distribution of visual zones in the work station

Another factor is the time frame during which vision occurs. The time of exposure will be greater or smaller depending on whether the object and the observer are static, or whether one or both of them are moving. The adaptive capacity of the eye to adjust automatically to the different illuminations of objects can also have considerable influence on visibility.

Light distribution; glare

Key factors in the conditions that affect vision are the distribution of light and the contrast of luminances. In so far as the distribution of light is concerned, it is preferable to have good general illumination instead of localized illumination in order to avoid glare. For this reason, electrical accessories should be distributed as uniformly as possible in order to avoid differences in luminous intensity. Constant shuttling through zones that are not uniformly illuminated causes eye fatigue, and with time this can lead to reduced visual output.

Glare is produced when a brilliant source of light is present in the visual field; the result is a diminution in the capacity to distinguish objects. Workers who suffer the effects of glare constantly and successively can suffer from eye strain as well as from functional disorders, even though in many cases they are not aware of it.

Glare can be direct when its origin is bright sources of light directly in the line of vision, or by reflection when light is reflected on surfaces with high reflectance. The factors involved in glare are:

1. Luminance of the source of light: The maximum tolerable lumi nance by direct observation is 7,500 cd/m². Figure 3 shows some of the approximate values of luminance for several sources of light.
2. Location of the source of light: This kind of glare occurs when the source of light is within a 45-degree angle of the observer’s line of sight, and will be minimized to the degree that the source of light is placed beyond that angle. Ways and methods of avoiding direct and reflective glare can be seen in the following figures (see figure 4).

Figure 3. Approximate values of luminance

Figure 4. Factors that affect glare

In general, there is more glare when sources of light are mounted at lower elevations or when installed in large rooms, because sources of light in large rooms or sources of light that are too low can easily fall within the angle of vision that produces glare.

3. Distribution of luminance among different objects and surfaces: The greater the differences in luminance are among the objects within the field of vision, the greater will be the glare created and the greater will be the deterioration in the capacity to see due to the effects on the adaptive processes of sight. The maximum recommended luminance disparities are:

• visual task—work surface: 3:1
• visual task—surroundings: 10:1

4. Time frame of the exposure: Even light sources with a low luminance can cause glare if the length of the exposure is prolonged too much.

Avoiding glare is a relatively simple proposition and can be achieved in different ways. One way, for example, is by placing grilles under the sources of illumination, or by using enveloping diffusers or parabolic reflectors that can direct light properly, or by installing the sources of light in such a way that they will not interfere with the angle of vision. When designing the work site, the correct distribution of luminance is as important as the illumination itself, but it is also important to consider that a distribution of luminance that is too uniform makes the three-dimensional and spatial perception of objects more difficult.

Lighting Systems

The interest in natural illumination has increased recently. This is due less to the quality of illumination it affords than to the well-being that it provides. But since the level of illumination from natural sources is not uniform, an artificial lighting system is required.

The most common lighting systems used are the following:

General uniform illumination

In this system light sources are spread out evenly without regard to the location of the work stations. The average level of illumination should be equal to the level of illumination required for the task that will be carried out. These systems are used mainly in workplaces where work stations are not fixed.

It should conform to three fundamental characteristics: The first is to be equipped with anti-glare devices (grilles, diffusers, reflectors and so on). The second is that it should distribute a fraction of the light toward the ceiling and the upper part of the walls. And the third is that the light sources should be installed as high as possible, to minimize glare and achieve illumination that is as homogeneous as possible. (See figure 5)

Figure 5. Lighting systems

This system tries to reinforce the general illumination scheme by placing lamps close to the work surfaces. These types of lamps often produce glare, and reflectors should be placed in such a way that they block the source of light from the direct sight of the worker. The use of localized illumination is recommended for those applications where visual demands are very critical, such as levels of illumination of 1,000 lux or greater. Generally, visual capacity deteriorates with the age of the worker, which makes it necessary to increase the level of general illumination or to second it with localized illumination. This phenomenon can be clearly appreciated in figure 6.

Figure 6. Loss of visual acuity with age

General localized illumination

This type of illumination consists of ceiling sources distributed with two things in mind—the illumination characteristics of the equipment and the illumination needs of each work station. This type of illumination is indicated for those spaces or work areas that will require a high level of illumination, and it requires knowing the future location of each work station in advance of the design stage.

Colour: Basic Concepts

Selecting an adequate colour for a worksite contributes a great deal to the efficiency, safety and general well-being of the employees. In the same way, the finish of the surfaces and of the equipment found in the work environment contributes to creating pleasant visual conditions and a pleasant work environment.

Ordinary light consists of electromagnetic radiations of different wavelengths that correspond to each of the bands of the visible spectrum. By mixing red, yellow and blue light we can obtain most of the visible colours, including white. Our perception of the colour of an object depends on the colour of the light with which it is illuminated and on the way the object itself reflects light.

Lamps can be classified into three categories depending on the appearance of the light they emit:

• colour with a warm appearance: a white, reddish light recommended for residential use
• colour with intermediate appearance: a white light recommended for worksites
• colour with a cold appearance: a white, bluish light recommended for tasks that require a high level of illumination or for hot climates.

Colours may also be classified as warm or cold according to their tonality (see figure 7).

Figure 7. Tonality of "warm" and "cold" colours

Contrast and temperature of different colours

Colour contrasts are influenced by the colour of the light selected, and for that reason the quality of illumination will depend on the colour of the light chosen for an application. The selection of the colour of light to be used should be made based on the task that will be carried out under it. If the colour is close to white, the rendition of colour and the diffusion of light will be better. The more light approaches the red end of the spectrum the worse the reproduction of colour will be, but the environment will be warmer and more inviting.

The colour appearance of illumination depends not only on the colour of light, but also on the level of luminous intensity. A colour temperature is associated with the different forms of illumination. The sensation of satisfaction with the illumination of a given environment depends on this colour temperature. In this way, for example, a 100 W incandescent filament light bulb has a colour temperature of 2,800 K, a fluorescent tube has a colour temperature of 4,000 K and an overcast sky has a colour temperature of 10,000 K.

Kruithof defined, through empirical observations, a diagram of well-being for different levels of illumination and colour temperatures in a given environment (see figure 8). In this way, he demonstrated that it is possible to feel comfortable in certain environments with low levels of illumination if the colour temperature is also low—if the level of illumination is one candle, for example, with a colour temperature of 1,750 K.

Figure 8. Comfort diagram as a function of illumination and colour temperatures

The colours of electric lamps can be subdivided into three groups related to their colour temperatures:

• daylight white—around 6,000 K
• neutral white—around 4,000 K
• warm white—around 3,000 K

Combination and selection of colours

The selection of colours is very relevant when we consider it together with those functions where identifying the objects that must be manipulated is important. It is also relevant when delimiting avenues of communication and in those tasks that require sharp contrast.

The selection of tonality is not as important a question as the selection of the proper reflective qualities of a surface. There are several recommendations that apply to this aspect of work surfaces:

Ceilings: The surface of a ceiling should be as white as possible (with a reflection factor of 75%), because light will then reflect from it in a diffuse way, dissipating darkness and reducing the glare from other surfaces. This will also mean a savings in artificial lighting.

Walls and floors: The surfaces of walls at eye level can produce glare. Pale colours with reflective factors of 50 to 75% tend to be adequate for walls. While glossy paints tend to last longer than matte colours, they are more reflective. Walls should therefore have a matte or semi-gloss finish.

Floors should be finished in slightly darker colours than walls and ceilings to avoid glare. The reflective factor of floors should be between 20 and 25%.

Equipment: Work surfaces, machinery and tables should have reflective factors of between 20 and 40%. Equipment should have a lasting finish of pure colour—light browns or greys—and the material should not be shiny.

The proper use of colours in the work environment facilitates well-being, increases productivity and can have a positive impact on quality. It can also contribute to better organization and the prevention of accidents.

There is a generalized belief that whitening the walls and ceilings and supplying adequate levels of illumination is all that can possibly be done as far as the visual comfort of employees is concerned. But these comfort factors can be improved by combining white with other colours, thus avoiding the fatigue and the boredom that characterize monochromatic environments. Colours also have an effect on a person’s level of stimulation; warm colours tend to activate and relax, while cold colours are used to induce the individual to release or liberate his or her energy.

The colour of light, its distribution, and the colours used in a given space are, among others, key factors that influence the sensations a person feels. Given the many colours and comfort factors that exist, it is impossible to set precise guidelines, especially considering that all these factors must be combined according to the characteristics and the requirements of a particular work station. A number of basic and general practical rules can be listed, however, that can help create a liveable environment:

• Bright colours produce comfortable, stimulating and serene feelings, while dark colours tend to have a depressing effect.
• Sources of warm-coloured light help reproduce warm colours well. Warm-coloured objects are more pleasing to the eye in warm light than in cold light.
• Clear and dull colours (like pastels) are very appropriate as background colours, while objects should have rich and saturated colours.
• Warm colours excite the nervous system and give the sensation that temperature is rising.
• Cold colours are preferable for objects. They have a calming effect and can be used to produce the effect of curvature. Cold colours help create the sensation that temperature is dropping.
• The sensation of colour of an object depends on the background colour and on the effect of the light source on its surface.
• Environments that are physically cold or hot can be tempered by using warm or cold lighting, respectively.
• The intensity of a colour will be inversely proportional to the part of the normal visual field that it occupies.
• The spatial appearance of a room can be influenced by colour. A room will seem to have a lower ceiling if its walls are painted a bright colour and the floor and ceiling are darker, and it will seem to have a higher ceiling if the walls are darker and the ceiling is bright.

Identifying objects through colour

The selection of colours can influence the effectiveness of lighting systems by influencing the fraction of light that is reflected. But colour also plays a key role when it comes to identifying objects. We can use brilliant and eye-catching colours or colour contrasts to highlight situations or objects that require special attention. Table 2 lists some of the factors of reflection for different colours and materials.

Table 2. Reflection factors of different colours and  materials illuminated with white light

In any case, identification by colour should be employed only when it is truly necessary, since identification by colour will work properly only if there are not too many objects that are highlighted by colour. The following are some recommendations for identifying different elements by colour:

• Fire and safety equipment: It is advisable to identify this equipment by placing a recognizable graphic on the nearest wall so that it can be found quickly.
• Machinery: The colouring of stop or emergency devices with bright colours on all machinery is critical. It is also advisable to mark with colour the areas that need lubrication or periodic maintenance, which can add ease and functionality to these procedures.
• Tubing and pipes: If they are important or carry dangerous substances the best advice is to colour them completely. In some cases it may be enough to colour only a line along their length.
• Stairways: In order to make descent easier, one band for every step is preferable to several.
• Risks: Colour should be used to identify a risk only when the risk cannot be eliminated. Identification will be much more effective if it is carried out according to a predetermined colour code.

Back

In general, pain is the main symptom of disorders of the leg, ankle and foot. It often follows exercise and may be aggravated by exercise. Muscle weakness, neurological deficiency, problems with fitting shoes, instability or stiffness of joints, and difficulties in walking and running are common problems in these disorders.

The causes of problems are usually multifactorial, but most often they arise from biomechanical factors, infections and/or systemic diseases. Foot, knee and leg deformities, bone and/or soft-tissue changes that follow an injury, excessive stress such as repetitive use, instability or stiffness and improper shoes are common causes of these symptoms. Infections may occur in the bony or soft tissues. Diabetes, rheumatic diseases, psoriasis, gout and blood circulation disturbances often lead to such symptoms in the lower limb.

Besides the history, a proper clinical examination is always necessary. Deformities, function disturbances, the blood circulation and the neurological state should be carefully examined. Analysis of gait may be indicated. Plain radiographs, CT, MRI, sonography, ENMG, vascular imaging and blood tests may contribute to the pathological and aetiological diagnosis and treatment.

Principles of treatment . The treatment should always be directed towards eliminating the cause. Except in traumas, the main treatment is usually conservative. The deformity will be, if possible, corrected by proper shoes and/or orthosis. Good ergonomic advice, including correction of wrong walking and running behaviour, is often beneficial. Diminishing of excessive loading, physiotherapy, anti-inflammatory drugs and in rare cases a short immobilization may be indicated. Redesign of work may be indicated.

Surgery may also be recommended in some acute traumas, especially for some persistent symptoms which have not benefited from conservative therapy, but specific medical advice is needed for each case.

Achilles Tendinitis

The disorder is usually due to overuse of the Achilles tendon, which is the strongest tendon in the human organism and is found in the lower leg/ankle. The tendon is exposed to excessive loading, especially in sports, resulting in pathological inflammatory and degenerative changes in the tendon and its surrounding tissues, bursae and paratenon. In severe cases a complete rupture may follow. Predisposing factors are improper shoes, malalignment and deformities of the foot, weakness or stiffness of the calf muscles, running on hard and uneven surfaces and intensive training. Achilles tendinitis occasionally occurs in some rheumatic diseases, after fractures of the crus or foot, in some metabolic diseases and following renal transplantation.

Pain and swelling in the region of the calcaneal tendon, the Achilles tendon, are rather common symptoms, especially in sportsmen. The pain is located in the tendon or its attachment to the calcaneum.

More men than women develop Achilles tendinitis. The symptoms are more frequent in recreational sports than in professional athletics. Running and jumping sports may especially lead to Achilles tendinitis.

The tendon is tender, often nodular, with swelling, and the tendon is fibrotic. Microruptures may be present. A clinical examination can be supported mainly by MRI and ultrasonography (US). MRI and US are superior to CT for demonstration of the region and quality of the soft-tissue changes.

Proper shoes in misalignment, orthotics, and advice in correct biomechanical training may prevent the development of Achilles tendinitis. When symptoms are present a conservative treatment is often successful: prevention of excessive training, proper shoes with heal lifts and shock absorption, physiotherapy, anti-inflammatory drugs, stretching and strengthening of the calf muscles.

Calcaneal Bursitis

Pain behind the heel, usually aggravated by walking, is often caused by a calcaneal bursitis, which frequently is associated with Achilles tendinitis. The disorder may be found in both heels and can occur at any age. In children, calcaneal bursitis is often combined with an exostosis or osteochondritis of the calcaneum.

In most cases improper footwear with narrow and hard back of the shoe is the cause of this disorder. In athletics excessive loading of the heel region, as in running, may provoke Achilles tendinitis and retrocalcaneal bursitis. A deformity of the back of the foot is a predisposing factor. There is usually no infection involved.

Upon examination, the tender heel is thickened and the skin may be red. There is often an inward bending of the hind part of the foot. Especially for differential diagnosis, radiographs are important and may reveal changes in the calcaneum (e.g., Sever’s disease, osteochondral fractures, osteophytes, bone tumours and osteitis). In most cases the history and the clinical examination will be supported by MRI or sonography. A retrocalcaneal bursogram can provide further insight into chronic cases.

The symptoms may subside without any treatment. In mild cases conservative treatment is usually successful. The painful heel should be protected with strapping and proper shoes with soft backs. An orthosis correcting the wrong position of the hind part of the foot may be valuable. A correction of the walking and running behaviour is often successful.

Surgical excision of the bursa and the impinging part of the calcaneum is indicated only when conservative treatment has failed.

Morton’s Metatarsalgia

Metatarsalgia is pain in the forefoot. It may be due to a neuroma of the plantar digital nerve, Morton’s neuroma. The typical pain is in the forefoot, usually radiating in the third and fourth toes, rarely in the second and third toes. The pain occurs on standing or walking at any age but is most frequent in middle-aged women. At rest the pain disappears.

The condition is often connected with flat forefoot and callosities. Compression of the metatarsal heads from side to side and of the space between the metatarsal heads may elicit pain. In plain radiographs the neuroma is not seen but other changes (e.g., bony deformities causing metatarsalgia) may be visible. MRI may reveal the neuroma.

Conservative treatment—proper shoes and pads—to support the anterior arch is often successful.

Tarsal Tunnel Syndrome

Burning pain along the sole of the foot and in all toes which may be due to compression of the posterior tibial nerve within the fibro-osseous tunnel under the flexor retinacle of the ankle, are all symptoms of tarsal tunnel syndrome. There are many conditions leading to compression of the nerve. The most common causes are bone irregularities, ankle fractures or dislocations, local ganglia or tumours, or bad footwear.

There may be loss of feeling in the areas where the medial and lateral plantar nerves lie, weakness and paralysis of foot muscles, especially the toe flexors, a positive Tinel’s sign and tenderness in the region of the nerve course.

A proper clinical examination of the function and the neurological and vascular state is essential. The syndrome may also be diagnosed by electrophysiological tests.

Compartment Syndromes of the Lower Limb

A compartmental syndrome is a result of prolonged high pressure of a closed intrafascial muscle space leading to markedly reduced blood circulation in the tissues. The high intracompartmental pressure is usually due to trauma (crush injuries, fractures and dislocations), but it will also result from overuse, from tumours and from infections. A tight cast may lead to a compartmental syndrome, as may diabetes and blood vessel disorders. The first symptoms are tense swelling, pain and curtailment of function which are not relieved when the leg is elevated, immobilized or treated with common drugs. Later on there will be paresthesia, numbness and paresis. In growing persons, a compartment syndrome may result in growth disturbances and deformities in the affected region.

If a compartment syndrome is suspected, a good clinical examination should be performed including that of the vascular, the neurological and the muscular state, the active and passive mobility of the joint and so on. Measurement of the pressure by multi-stick catheterization of the compartments should be performed. MRI, Doppler investigation and sonography may be helpful in the diagnosis.

Foot and Ankle Region Tenosynovitises

Of many symptoms in the foot, pain following tenosynovitis is rather common, especially in the ankle region and the longitudinal arch. The cause of the synovitis may be deformities of the foot, such as planovalgus, excessive stress, improper shoe fit, or sequelae to fractures and other injuries, rheumatological disorders, diabetes, psoriasis and gout. Synovitis may occur in many tendons, but the Achilles tendon is most often affected. Only rarely does tendinitis involve infection. A medical history and clinical examination are essential in the diagnosis of synovitis. Local pain, tenderness and painful movement are the main symptoms. Plain radiographs that show the bone changes and MRI, especially for changes in the soft tissues, are needed.

Ergonomic advice is needed. Proper shoes, correction of the walking and running habits and prevention of excessive stress situations on the job are usually beneficial. A short period of rest, immobilization in a cast and anti-inflammatory drugs are often indicated.

Hallux Valgus

Hallux valgus consists of extreme deviation of the first joint of the great toe towards the midline of the foot. It is often associated with other foot disorders (varus of the first metatarsal; flat foot, pes planotransversus or planovalgus). Hallux valgus may occur at any age, and it is seen more commonly in women than in men. The condition is in most cases familial, and it is often due to the wearing of improperly fitted shoes, such as ones with high heels and narrow pointed toe boxes.

The metatarsal joint is prominent, the first metatarsal head is enlarged, and there may be a (often inflamed) bursa bunion over the medial aspect of the joint in this condition. The great toe frequently overrides the second toe. The soft tissues of the toe are often changed due to the deformity. The range of extension and flexion of the metatarsophalangeal joint is usually normal, but it may be stiff due to osteoarthritis (hallux rigidus). In the vast majority of cases the hallux valgus is painless and requires no treatment. In some cases, however, hallux valgus causes shoe fitting problems and pain.

The treatment should be individualized according to the age of the patient, the degree of the deformity and the symptoms. Especially with adolescents and cases with mild symptoms, conservative treatment is recommended—proper shoes, insoles, pads to protect the bunion and so on.

Surgery is reserved especially for adult patients with severe shoe-fitting problems and pain, whose symptoms are not relieved by conservative treatment. The surgical procedures are not always successful, and therefore mere cosmetic factors should not be a real indication for surgery; but there is a great range of opinions regarding the usefulness of the approximately 150 different surgical procedures for hallux valgus.

Fascitis Plantaris

The sufferer feels pain under the heel, especially on long standing and walking. The pain radiates frequently to the sole of the foot. Plantar fascitis may occur at any age, but it is most frequent in middle-aged persons. The patients are often obese. It is also a rather common disorder in people who engage in sports. Often the foot has a flattened longitudinal arch.

There is local tenderness especially beneath the calcaneum at the attachment of the plantar fascia. All the fascia may be tender. On x ray a bony spur is seen in the calcaneum in about 50% of the patients, but it is also present in 10 to 15% of symptomless feet.

The causes of fascitis plantaris are not always clear. An infection, particularly gonorrhaea, rheumatoid arthritis and gout may cause the symptoms. Most frequently no specific diseases are connected to the condition. Increased pressure and tension of the fascia may be the main cause of the tenderness. The calcaneal spur may be a result of overusing of the fascia plantaris. It is probably not the primary cause of the calcaneal tenderness, because so many patients with those symptoms have no calcaneal spur and many with calcaneal spur are symptomless.

Back

The hip joint is a ball-and-socket joint surrounded by ligaments, strong muscles and bursae. The joint is weight bearing and has both high intrinsic stability and a wide range of motion. In young people pain in the hip region usually originates in the muscles, tendon insertions or bursae, while in older people, osteoarthrosis is the predominant disorder causing hip pain.

The knee is a weight-bearing joint that is important for walking, standing, bending, stooping and squatting. The knee is rather unstable and depends for support on ligaments and strong muscles as shown in figure 1. There are two joints in the knee, the femorotibial and the femoropatellar. On both inner and outer side of the joint there are strong ligaments, and in the centre of the femorotibial joint are the cruciate ligaments, which give stability and assist in the normal mechanical function of the knee. The menisci are curved, fibrocartilaginous structures that lie between the femoral (femoral condyles) and the tibial bones (tibial plateau). The knee joint is both stabilized and empowered by muscles that originate above the hip joint and at the shaft of the femur and are inserted upon bony structures below the knee joint. Around the knee joint there is a synovial capsule, and the joint is protected by several bursae.

Figure 1. The knee.

All these structures are easily hurt by trauma and overuse, and medical treatment for knee pain is rather common. Osteoarthrosis of the knee is a common disorder among the elderly, leading to pain and disability. In younger people, patellar bursitis and patellofemoral pain syndromes like a painful pes anserinus are rather common.

Osteoarthrosis

Osteoarthrosis (OA) is a common degenerative joint disorder in which the cartilage is more or less destroyed and the structure of the underlying bone is affected. Sometimes it is accompanied by few symptoms, but usually OA causes suffering, changes in ability to work and a decreased quality of life. Changes in the joint can be seen on x ray, and an OA sufferer usually seeks medical care because of pain, which is present even at rest, and a diminished range of motion. In severe cases, the joint may become totally stiff, and even destroyed. Surgery to replace a destroyed joint and replace it with a prosthesis is well developed today.

Studying the causes of osteoarthrosis of the hip is difficult. The onset of the disorder is usually hard to pinpoint; the development is usually slow and insidious (that is, one doesn’t necessarily know it is happening). The end point, for research purposes, can be different things, varying from slight changes in x rays to symptomatic disorders that require surgery. Indeed the end points used to identify the condition may differ because of different traditions in different countries, and even between different clinics in the same town. These factors cause problems in the interpretation of research studies.

Epidemiological research tries to identify associations between exposures such as physical load, and outcomes, such as osteo-arthrosis. When combined with other knowledge, it is possible to find associations that could be considered causal, but the cause-effect chain is complicated. Osteoarthrosis is common in every population, and one must remember that the disorder exists among persons with no known hazardous exposure, while there are healthy subjects in the group with high and well-known harmful exposure. Unknown paths between exposure and disorder, unknown health factors, genetics and selection forces may be a few of the contributors to that.

Individual risk factors

Age: The occurrence of arthrosis increases with age. X-ray investigations of osteoarthrosis of different joints, mainly the hip and the knee, have been made in different populations and the prevalences found to vary. The explanation might be ethnic differences or variations in investigation techniques and diagnostic criteria.

Congenital and developmental diseases and changes: Early changes in the joint, such as congenital malformations, those caused by infections and so on, lead to an earlier and faster progression of osteoarthrosis of the hip. Knock-knees (varus) and bandy-legs (valgus) put an uneven distribution of forces on the knee joint, for example, which can have some importance for arthrosis development.

Heredity: Hereditary factors are present for osteoarthrosis. For example, osteoarthrosis of the hip is a rare disease among people of Asian origin but more common among Caucasians, which suggests a hereditary factor. Osteoarthrosis in three or more joints is called generalized osteoarthrosis and has a hereditary pattern. The hereditary pathway for osteoarthrosis of the knee is not very well known.

Overweight: Overweight can probably cause osteoarthrosis of the knee and hip. The relationship between overweight and knee osteoarthrosis has been shown in large epidemiological studies of the general population, such as the National Health and Nutrition Examination Survey (NHANES) and Framingham study in the United States. The association was strongest for women but existed even for men (Anderson and Felson 1988; Felson et al. 1988).

Trauma: Accidents or causes of trauma or injury, especially those that interfere with the mechanics and circulation of the joint and ligament, can give rise to an early osteoarthrosis.

Sex and oestrogen use: Osteoarthrosis of the hip and knee seems to be equally distributed among men and women. From a study on female participants in the Framingham study, it was concluded that oestrogen use in women is associated with a modest but insignificant protective effect against osteoarthrosis of the knee (Hannan et al. 1990).

Mechanical load

Experimental studies in monkeys, rabbits, dogs and sheep have shown that compression forces on a joint, especially when it is held in an extreme position, with or without simultaneous shifting loads, can lead to changes in the cartilage and bone similar to those of osteoarthrosis in human beings.

Sports activities: Participation in sports can increase the load on different joints. The risk of trauma is also increased. On the other hand, however, good muscle function and coordination are developed at the same time. Few data are available as to whether participating in sports prevents trauma or is harmful to the joints. Data drawn from good scientific studies are very limited, and some are described here. Several studies of soccer players have shown that both professionals and amateurs have more osteoarthrosis of the hip and knee than the general male population. For example, one Swedish study of 50- to 70-year-old men with a severe osteoarthrosis who were compared with healthy men in the same age group, showed that the men with osteoarthrosis had been more heavily involved in sports activities in their youth. Track and field, racket sports, and soccer seemed to be most harmful (Vingård et al. 1993). In the scientific literature there are other studies that have not shown any differences between athletes and those who do not participate in sports. However most of them are performed on still active athletes and are thus not conclusive.

Workload factors

The aetiology of osteoarthrosis of the knee and hip is, as for all diseases, complex and multifactorial. Recent well-performed studies have shown that physical load on the joint from occupational exposures will play a role as a contributing cause for the development of premature osteoarthrosis.

Most epidemiological studies concerning physical workload are cross-sectional and carried out on occupational groups without making individual exposure assessments. These serious methodological problems make generalizing the results of such studies extremely difficult. Farmers have been found to have more osteoarthrosis of the hip than other occupational groups in several studies. In a Swedish study of 15,000 farmers, farmers’ wives and other farm workers were asked about past x-ray examinations in which the hip joint could be seen. Among the 565 men and 151 women who had been examined, hip joints were studied using the same criteria and the same investigator as in a population study from Sweden 1984. The distribution of osteoarthrosis of the hip among male farmers and the male population of Malmö is shown in table 1 (Axmacher and Lindberg 1993).

Table 1. Prevalence of primary osteoarthrosis of the hip among male farmers and population of different age groups in the city of Malmö.

N = Number of men studied; cases = men with osteoarthrosis of the hip.
Source: Axmacher and Lindberg 1993.

In addition to farmers, construction workers, food-processing workers (grain-mill workers, butchers and meat preparers), firefighters, mail carriers, shipyard workers and professional ballet dancers have all been found to be at an increased risk of hip osteoarthrosis. It is important to realize that an occupational title alone does not adequately describe the stress on a joint—the same job type can mean different loads for different workers. Further, the load of interest in a study is the exact pressure placed on a joint. In a study from Sweden, physical workload has been quantified retrospectively through individual interviews (Vingård et al. 1991). Men with high physical load exposures due to their occupations up to the age of 49 had more than double the risk for developing osteoarthrosis of the hip compared to those with low exposure. Both dynamic exposures, such as heavy lifting, and static exposure, such as prolonged sitting in a twisted position, seemed to be equally harmful to the joint.

The risk of knee osteoarthrosis has been found to be increased in coal miners, dockers, shipyard workers, carpet and floor layers and other construction workers, firefighters, farmers and cleaners. Moderate to heavy physical demands at work, knee bending and traumatic injury increase the risk.

In another English study from 1968, dockers were found to have more osteoarthrosis of the knee than civil servants in sedentary occupations (Partridge and Duthie 1968).

In Sweden, Lindberg and Montgomery investigated workers in a shipyard and compared them to office workers and teachers (Lindberg and Montgomery 1987). Among shipyard workers 3.9% had gonarthrosis, compared to 1.5% among office workers and teachers.

In Finland, Wickström compared concrete reinforcement workers with painters, but no differences in disability from the knees were found (Wickström et al. 1983). In a later Finnish study, knee disorders in carpet and floor layers and painters were compared (Kivimäki, Riihimäki and Hänninen 1992). Knee pain, knee accidents, and treatment regimes for the knees, as well as osteophytes around the patella, were more common among carpet and floor layers than among the painters. The authors suggest that kneeling work increases the risk of knee disorders and that the changes observed in x rays might be an initial sign of knee degeneration.

In the United States, factors associated with osteoarthrosis of the knee in the first National Health and Nutrition Examination Survey (NHANES 1) were examined for a total of 5,193 men and women aged 35 to 74 years, 315 of whom had x-ray-diagnosed osteoarthrosis of the knee (Anderson 1988). In investigating occupational load the authors characterized the physical demands and knee-bending stress from occupational titles in US Department of Labor Dictionary of Occupational Titles. For both men and women, for those whose jobs were described as involving a lot of knee-bending, the risk for developing an osteoarthrosis of the knee was more than double that for those without such jobs. When controlling for age and weight in the statistical analysis, they found that 32% of the osteoarthrosis of the knee occurring in these workers was attributable to occupation.

In the Framingham study in the United States, subjects from Framingham, a town outside Boston, have been followed in an epidemiological study for more than 40 years (Felson 1990). Occupational status was reported for the years 1948–51 and 1958–61 and the results of x rays looking for radiographic osteo- arthrosis of the knee during the years 1983–85. Each subject’s job was characterized by its level of physical demand and whether the job was associated with knee-bending. This study also found that the risk for developing osteoarthrosis of the knee was doubled for those with a lot of knee bending and at least medium physical demands in their occupation.

In a study from California the roles of physical activity, obesity and knee injury on the development of severe osteoarthrosis of the knee was evaluated (Kohatsu and Schurman 1990). Forty-six people with gonarthrosis and 46 healthy people from the same community were studied. The persons with osteoarthrosis were two to three times more likely than the controls to have performed moderate to heavy work earlier in life and 3.5 times more likely to have been obese at the age of 20. They were almost five times more likely to have had a knee injury. There was no difference in the leisure time activities reported in the two groups.

In a register-based cohort study from Sweden (Vingärd et al. 1991) subjects born between 1905 and 1945, living in 13 of the 24 counties in Sweden in 1980 and reporting that they held the same blue-collar occupation in the censuses of 1960 and of 1970, were studied. The blue-collar occupations reported were then classified as to whether they were associated with high (more than average) or low (less than average) load on the lower extremity. During 1981, 1982 and 1983 it was determined whether the study population sought hospital care for osteoarthrosis of the knee. Firefighters, farmers and construction workers had an elevated relative risk among men to develop osteoarthrosis of the knee. Among women, cleaners were found to be at greater risk.

Chondromalacia patellae

A special case of osteoarthrosis is chondromalacia patellae, which often starts in the young. It is a degenerative change in the cartilage on the back of the patella bone. The symptom is pain in the knee, especially while bending it. Among sufferers, the patella is very tender when tapped, and especially if pressure is put on it. The treatment is quadriceps muscle training and, in severe cases, surgery. The connection to occupational activity is unclear.

Patellar bursitis

In the knee, there is a bursa between the skin and the patella. The bursa, which is a sac containing fluid, can be subject to mechanical pressure during kneeling and thus become inflamed. Symptoms are pain and swelling. A substantial amount of serous fluid can be aspirated from the bursa. This disorder is rather common among occupational groups that do a lot of kneeling. Kivimäki (1992) has investigated soft-tissue changes in the front of the knee using ultrasonography in two occupational groups. Among carpet and floor layers 49% had thickening of the prepatellar or superficial infrapatellar bursa, compared to 7% among painters.

Pes anserinus bursitis

The pes anserinus consists of the tendons of the sartorius, semimembranous and gracilis muscles at the inner aspect of the knee joint. Under the insertion point of these tendons, there is a bursa that can be inflamed. Pain is increased by forceful extension of the knee.

Trochanter bursitis

The hip has many bursae that surround it. The trochanteric bursa lies between the tendon of the gluteus maximus muscle and the posterolateral prominence of the greater trochanter (the other side of the hip). Pain in this area is usually called trochanter bursitis. Sometimes it is a true bursitis. The pain can radiate down the thigh and may simulate sciatic pain.

Theoretically it is possible that a special occupational posture can cause the disorder, but there are no scientific investigations.

Meralgia paresthetica

Meralgia paresthetica belongs to the entrapment disorders, and the cause is probably an entrapment of the nervus cutaneus femoris lateralis where the nerve comes out between muscles and fasciae above the edge of the pelvis (spina iliaca anterior superior). The sufferer will have pain along the front and lateral side of the thigh. The disorder can be rather tricky to cure. Different remedies, from pain killers to surgery, have been used with varying success. Since there are occupational exposures which cause pressure against the nerve, so this condition may be an occupational disorder. Anecdotal accounts of this exist, but there are no epidemiological investigations available that verify it.

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