Work-related musculoskeletal disorders (WMSDs), which are often soft-tissue injuries, occur when there is a mismatch between the physical requirements of the job and the physical capacity of the human body. They are the leading cause of disability for people in their working years. Specific risk factors associated with WMSDs include repetitive movements, heavy lifting, twisting, forceful exertion, kneeling, working in awkward positions, contact stress, working overhead, over-reaching, gripping, squatting, vibration, bending, awkward posture and rapid hand and wrist movement.
The three primary risk factors that have been associated with WMSDs are repetitious movement, awkward postures, and high force levels.
More than 100 different WMSDs can result from repetitive motions that produce wear and tear on the body. Back pain, knee pain, shoulder pain, foot and ankle pain, wrist tendinitis and carpal tunnel syndrome may all stem from work-related overuse.
Some of the signs and symptoms of WMSDs include:
- Numbness or a burning sensation in the hand
- Reduced grip strength in the hand
- Swelling or stiffness in the joints
- Pain in wrists, forearms, elbows, neck, or back followed by discomfort
- Reduced range of motion in the shoulder, neck, or back
- Foot, leg and knee pain
- Aching or tingling
- Cramping
- Weakness
- Tension stress headaches and related ailments
Repetitive movements can disturb the delicate balance of muscles, tendons, and ligaments and cause cumulative trauma disorders ( CTDs), also known as repetitive strain injuries (RSIs). Nerves can be compromised through repetitive movements. Repeated motions can result in compression or "entrapment "of nerves. Compression can be caused by tight muscles, inflammation of surrounding tissues, or misalignment of the nerve.
Some common nerve injuries/syndromes that can result from repetitive movements include thoracic outlet, radial tunnel, cubital tunnel and carpal tunnel syndromes.
Tendons also can be affected by repetitive motions. They attach muscle to bone, and are connective tissues that contain little stretch or rebound. If they are stressed beyond their strength by overuse, or maintaining a static or prolonged position, they can get tiny tears in them. Friction from overuse can also cause inflammation. This causes a condition known as tendinitis.
Tendinitis occurs most often in the flexor and extensor tendons of the fingers, thumb, forearm, elbow or shoulder. Symptoms range from specific aches, stiffness, tightness and burning sensations, to a deep nonspecific pain. Grasp can be impaired to the point where you have difficulty holding on to objects.
The tendons of the wrist and hand are very small and are at a high risk for injury when overused. Although naturally stronger and more durable, the larger tendons in the shoulders can be affected if the arms are held out in front, or off to the side too long, or excessive reaching is done while working. Tennis elbow, or lateral epicondylitis, affects the tendons of the finger extensor muscles at the outside of the elbow. Golfer's elbow, or medical epicondylitis, affects the tendons of the finger flexor muscles at the inside of the elbow. Muscles can be strained by overuse resulting in tiny tears in the muscles. These tiny tears form scar tissue and contribute to inflammation and muscle stiffness. A diffuse, achy pain can result in what's called myofascial pain. Painful nodules, or tender spots called trigger points, can also occur in overused muscles.
Trigger points can occur in almost any muscle. When you press a sore spot, the pain can travel out to a distant area and then recede. This is called a referral pattern. The site of the trigger point is usually distant from the site of the referred pain. Muscles in the neck refer pain to the head, shoulders, upper back and hand. Muscles in the arms can refer pain to the neck, shoulders, elbows, wrists and hands. Sleep patterns are often disrupted by muscle pain. You wake up feeling stiff and tired even when you think you have had enough sleep. This disruption of sleep, and increased discomfort, can increase fatigue levels that result from working with overused muscles.
Joints can get stiff and dysfunctional if they are being held in one position for multiple hours day in and day out. The cervical and lumbar spine joints are particularly susceptible to strain when the spine is held in prolonged, awkward postures. Awkward posture can strain the ligaments in the spine that support the joints and create stiffness and inflammation in a joint.
