Work-related musculoskeletal disorders (WMSDs) are a group of painful disorders of muscles, tendons, and nerves. Carpal tunnel syndrome, tendonitis, thoracic outlet syndrome, and tension neck syndrome are examples. Work activities which are frequent and repetitive, or activities with awkward postures cause these disorders which may be painful during work or at rest.Almost all work requires the use of the arms and hands. Therefore, most WMSD affect the hands, wrists, elbows, neck, and shoulders. Work using the legs can lead to WMSD of the legs, hips, ankles, and feet. Some back problems also result from repetitive activities.WMSDs are very difficult to define within traditional disease classifications. These disorders have received many names, such as:•Repetitive motion injuries.•Repetitive strain injuries.•Cumulative trauma disorders.•Occupational cervicobrachial disorders.•Overuse syndrome.•Regional musculoskeletal disorders.•Soft tissue disorders.Most of the names do not accurately describe the disorders. For example, the term "repetitive strain injuries" suggests that repetition causes these disorders, but awkward postures also contribute. These terms are used synonymously, and in the absence of agreement, WMSD is used in this document.WMSDs are recognized as leading causes of significant human suffering, loss of productivity, and economic burdens on society. The data available are limited and does not represent the magnitude of the problem because there is a great deal of under-reporting of these types of injuries.WMSDs arise from ordinary arm and hand movements such as bending, straightening, gripping, holding, twisting, clenching and reaching. These common movements are not particularly harmful in the ordinary activities of daily life. What makes them hazardous in work situations is the continual repetition, often in a forceful manner, and most of all, the speed of the movements and the lack of time for recovery between them.WMSDs are associated with work patterns that include:•Fixed or constrained body positions.•Continual repetition of movements.•Force concentrated on small parts of the body, such as the hand or wrist.•A pace of work that does not allow sufficient recovery between movements.Generally, none of these factors acts separately to cause WMSD. WMSDs commonly occur as a result of a combination and interaction among them.Heat, cold and vibration also contribute to the development of WMSD.Pain is the most common symptom associated with WMSDs. In some cases there may be joint stiffness, muscle tightness, redness and swelling of the affected area. Some workers may also experience sensations of "pins and needles," numbness, skin colour changes, and decreased sweating of the hands.WMSDs may progress in stages from mild to severe:•Early stage: Aching and tiredness of the affected limb occur during the work shift but disappear at night and during days off work. No reduction of work performance.•Intermediate stage: Aching and tiredness occur early in the work shift and persist at night. Reduced capacity for repetitive work.•Late stage: Aching, fatigue, and weakness persist at rest. Inability to sleep and to perform light duties.