Common MSDs | Ergonomics

The most common MSDs in the workplace are tendon disorders such as tendinitis, tenosynovitis, De Quervain’s disease, trigger finger, Raynaud’s syndrome, and carpal tunnel syndrome. Tendon disorders often occur at or near the joints where the tendons rub against ligaments and bones. The most frequently noted symptoms of tendon disorders are a dull aching sensation over the tendon, discomfort with specific movements, and tenderness to the touch. Recovery is usually slow and the condition may easily become chronic if the cause is not eliminated.

Tendinitis

Tendinitis is tendon inflammation that occurs when a muscle or tendon is repeatedly tensed from overuse, vibration, or unaccustomed usage of the wrist and shoulder. With further exertion, some of the fibers that make up the tendon can actually fray or tear apart. The tendon becomes thickened, bumpy, and irregular in certain areas of the body, such as the shoulder, and the injured area may calcify. Without rest and sufficient time for the tissues to heal, the tendon may be permanently weakened. Tendinitis is common among power press operators, welders, painters, and assembly line workers in the automobile, appliance, and electronic production industries.

Tenosynovitis

Tenosynovitis is an inflammation or injury to the synovial sheath surrounding the tendon. These sheaths secrete synovial fluid which acts as a lubricant to reduce friction during movement. Repetitive motion using the hands and wrists may provoke an excessive secretion of synovial fluid, with the sheath becoming swollen and painful. Repetitions exceeding 1,500 to 2,000 per hour are known to produce symptoms associated with tendon sheath irritation in the hands. Tenosynovitis often affects workers in meatpacking and poultry processing. Also those whose tasks require buffing, grinding, sanding, sawing, and punch press operations.

DeQuervain's Disease

In DeQuervain’s disease, the tendon sheath of the thumb is inflamed. This disease is attributed to excessive friction between two thumb tendons and their common sheath. Twisting and forceful gripping motions with the hands, similar to a clothes-wringing movement, can place sufficient stress on the tendons to cause DeQuervain’s disease. Tasks involving these kinds of motions are frequently performed by butchers, housekeepers, packers, seamstresses, and cutters.

Trigger Finger

Trigger finger, another tendon disorder, is attributed to the creation of a groove in the flexing tendon of the finger. If the tendon becomes locked in the sheath, attempts to move that finger will cause snapping and jerking movements. The palm side of the fingers is the usual site for trigger finger. This disorder is often associated with using tools that have handles with hard or sharp edges or whose handles are too far apart for the user’s hand. Meatpackers, poultry workers, electronic assemblers, and carpenters are at risk of developing trigger finger.

Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS), a disorder affecting the hands and wrists, has probably received more attention in recent years than any other musculoskeletal disorder. CTS is the compression and entrapment of the median nerve where it passes through the wrist into the hand in the carpal tunnel. The median nerve is the main nerve that extends down the arm to the hand and provides the sense of touch in the thumb, index finger, middle finger, and half of the fourth or ring finger.

When irritated, tendons housed inside the narrow carpal tunnel swell and press against the nearby median nerve. The pressure causes tingling, numbness, or severe pain in the wrist and hand. The pain is often experienced at night. The pressure also results in a lack of strength in the hand and an inability to make a fist, hold objects, or perform other manual tasks. If the pressure continues, it can damage the nerve, causing permanent loss of sensation and even partial paralysis.

Carpal tunnel syndrome develops in the hands and wrists when repetitive or forceful manual tasks are performed over a period of time. Workers need to be aware of the symptoms and causes of CTS and what to do about them. Initially, they may have fatigue and pain which develops during the work day and disappears overnight with no physical symptoms. After a length of time, fatigue and pain develop earlier in the day, some physical symptoms such as clumsiness may occur which affect work performance, and there may be no overnight recovery.

When the case becomes full-blown, there is constant fatigue and pain with no overnight recovery and disturbed sleep results. At this point, work performance is inhibited to the extent of requiring off-duty time or light/restricted duty. Often workers do not associate their pain with their work because symptoms may only occur during evening or off-duty hours. When they finally seek medical help, surgery may be necessary and the road to recovery will take more time than anticipated.

Raynaud's Syndrome

Raynaud’s syndrome, or white finger, occurs when the blood vessels of the hand are damaged as a result of repeated exposure to vibration for long periods of time. The skin and muscles are unable to get the necessary oxygen from the blood and eventually die. Common symptoms include:

• Intermittent numbness and tingling in the fingers;

• Skin that turns pale, ashen and cold; and

• Eventual loss of sensation and control in the fingers and hands.

Raynaud’s syndrome is associated with the use of vibrating tools over time, such as pneumatic hammers, electric chain saws, and gasoline powered tools. After long-term exposure, the blood vessels in the fingers may become permanently damaged. This condition is also intensified when the hands are exposed to extremely cold temperatures.

There is no medical remedy for white finger. If the fingers are fairly healthy, the condition may improve if exposure to vibration stops or is reduced. Job activities that can lead to Raynaud’s Syndrome include chain sawing, jack hammering, use of vibrating tools, sanding, painting, and using a tool too small for the hand, often in a cold environment.

Other types of vibration may affect the entire body, producing overall fatigue and potential permanent damage. Vibration in conjunction with prolonged sitting may also result in degenerative changes in the spine. For example, drivers of tractors, trucks, buses, construction machinery, and other heavy equipment may suffer from low back pain, and permanent abdominal, spinal and bone damage.

Back Disorders

Pulled or strained muscles, ligaments, tendons, and disks are perhaps the most common back problems and may occur in almost half of the work force at least once during their lifetime. The majority of workplace back disorders result from chronic, or long-term injury to the back rather than from one specific incident. Only about four percent of back injuries are associated with a single traumatic incident.

Back disorders are frequently caused by the cumulative effects of faulty body mechanics:

• Excessive or repetitive twisting, bending, and reaching;

• Carrying, moving, or lifting loads that are too heavy or too large;

• Staying in one position for too long;

• Poor physical condition; or

• Awkward posture.

When back muscles or ligaments are injured from these repetitive pulling and straining activities, the back muscles, disks, and ligaments can become scarred and weakened and lose their ability to support the back, making additional injuries more likely.

Prolonged sitting stresses the body, particularly the lower back and the thighs, and may cause the lower back (lumbar) region to bow outward if there is inadequate support. This abnormal curvature (called kyphosis) can lead to painful lower back problems, a common complaint among office workers.

Other factors which are contributors to back injuries include the natural degeneration of the back due to aging, inactivity both at work and at home, seasonal activity undertaken without prior physical conditioning, stress, and vibration.