Pain is the chief symptom of most musculoskeletal disorders. The pain may be mild or severe, local or widespread (diffuse). Although pain may be acute and short-lived, as is the case with most injuries, pain may be ongoing with chronic illnesses, such as rheumatoid arthritis.
Musculoskeletal pain can be caused by damage to bones, joints, muscles, tendons, ligaments, bursae, or nerves. Injuries are the most common cause. If no injury has occurred or if pain persists for more than a few days, then another cause is often responsible.
Bone pain is usually deep, penetrating, or dull. It commonly results from injury. Other less common causes of bone pain include bone infection (osteomyelitis) and tumors.
Muscle pain is often less intense than that of bone pain but can be very unpleasant. For example, a muscle spasm or cramp (a sustained painful muscle contraction) in the calf is an intense pain that is commonly called a charleyhorse. Pain can occur when a muscle is affected by an injury, an autoimmune reaction (for example, polymyositis or dermatomyositis), loss of blood flow to the muscle, infection, or invasion by a tumor.
Tendon and ligament pain is often less intense than bone pain. It is often worse when the affected tendon or ligament is stretched or moved. Common causes of tendon pain include tendinitis, tenosynovitis, lateral and medial epicondylitis, and tendon injuries. Common causes of ligament pain include injuries (sprains).
Fibromyalgia may cause pain in the muscles, tendons, or ligaments. The pain is usually in multiple locations and may be difficult to describe precisely. Affected people usually have other symptoms.
Virtually all joint injuries and diseases produce a stiff, aching pain, often referred to as “arthritic” pain. The pain is worse when the joint is moved and may range from mild to severe. With some conditions, there may be swelling of the joint along with the pain. Joint inflammation (arthritis) is a common cause of joint pain. There are many types of arthritis, including rheumatoid and other types of inflammatory arthritis, osteoarthritis, infectious arthritis, and arthritis due to gout or pseudogout. Other causes of joint pain include autoimmune and vasculitic disorders (for example, systemic lupus erythematosus, polymyalgia rheumatica, and polyarteritis nodosa), avascular necrosis of bone, and injuries (for example, dislocations, sprains, and fractures affecting the portion of the bone inside the joint). Sometimes, pain originating in structures near the joint, such as tendons and bursae, seems to be coming from the joint.
Some musculoskeletal disorders cause pain by compressing nerves. These conditions include the “tunnel syndromes” (for example, carpal tunnel syndrome, cubital tunnel syndrome, and tarsal tunnel syndrome). The pain tends to radiate along the path supplied by the nerve and may be burning.
Bursal pain can be caused by bursitis or fibromyalgia. Usually, bursal pain is worse with movement involving the bursa. There may be swelling.
Sometimes, pain that seems to be musculoskeletal is actually caused by a disorder in another organ system. For instance, shoulder pain may be caused by a disorder affecting the spleen or gallbladder. Back pain may be caused by an abdominal aortic aneurysm. Arm pain may be caused by a heart attack (myocardial infarction). Additionally, sometimes pain that seems to be coming from one part of the musculoskeletal system actually comes from another part. For instance, knee pain in an adolescent may be caused by a disorder of the hip called slipped capital femoral epiphysis.
Evaluation and Treatment
Sometimes, the type of pain suggests where the pain has originated. For example, pain that worsens with motion suggests a musculoskeletal disorder. Pain with muscle spasm suggests that pain is caused by a muscle disorder. The site of swelling or the location of tenderness when the doctor palpates the area (for example, a joint, ligament, or bursa) often indicates the source of pain. However, often these characteristics of pain do not indicate its origin or cause. Thus, doctors usually base a specific diagnosis on the presence of other symptoms and often on the results of laboratory tests and x-rays. For example, Lyme disease often produces joint pain and a bull’s eye—like skin rash; blood tests show antibodies to the bacteria that cause Lyme disease. Gout is characterized by a sudden attack of pain, swelling, and redness in the joint at the base of the big toe or other joints; tests of the joint fluid generally show the presence of uric acid crystals.
Blood tests are useful only in supporting the diagnosis made by the doctor after an examination. A diagnosis is not made or confirmed by a blood test alone. Examples of such blood tests include rheumatoid factor and antinuclear antibodies, which are used to help diagnose many of the common causes of arthritis, such as rheumatoid arthritis and systemic lupus erythematosus. Usually, such tests are recommended only if symptoms specifically suggest such a disorder or are persistent or unusually severe.
X-rays are primarily used to take images of bones; they do not show muscles, tendons and ligaments. X-rays are usually taken if the doctor suspects a fracture or, less commonly, a bone tumor or infection or to look for changes that confirm a person has a certain kind of arthritis (for example, rheumatoid arthritis or osteoarthritis).
A computed tomography (CT) scan is more sensitive than an x-ray and is often used to obtain more detail about a fracture or bone problem that was found with plain x-rays.
Unlike plain x-rays, magnetic resonance imaging (MRI) can identify abnormalities of soft tissues such as muscles, bursae, ligaments, and tendons. Thus, MRI may be used when the doctor suspects damage to a major ligament or tendon, or damage to important structures inside a joint.
Pain is usually best relieved by treating its cause. In addition, the doctor may recommend analgesics (see Pain: Treatment) such as acetaminophen Some Trade Names
, nonsteroidal anti-inflammatory drugs (NSAIDs), or, if pain is severe, opioids. Depending on the cause, applying cold or heat or immobilizing the joint may help relieve musculoskeletal pain.
A person may have difficulty moving all or part of the body.
Moving may be difficult because of disorders that restrict joint motion or that produce weakness. Movement may also be limited when motion causes pain. Certain nervous system abnormalities interfere with movement without causing pain or weakness. For example, Parkinson’s disease causes muscle stiffness, tremor, and difficulty initiating movement.
Joint Disorders: A joint that is stiffened by scar tissue from a previous injury can have limited range and speed of motion. When a normal joint is not used, it may stiffen. For example when a person’s arm is paralyzed by a stroke or even placed in a sling for a period of time, the joints in the shoulder and elbow may develop scar tissue that freezes the joint in place if the arm is not regularly flexed and stretched. Fluid that accumulates in a joint from arthritis or an acute injury can interfere with joint motion. A piece of torn cartilage from an injury (typically in the knee) may block joint motion.
Weakness: Although many people complain of weakness when they feel tired or run down, true weakness means that full effort does not generate normal muscle contractions. Normal voluntary muscle contraction requires that the brain generate a signal that then travels through the spinal cord and nerves to reach a normally functioning muscle. Therefore, true weakness can result from injury or disease affecting the nervous system, muscles, or connections between them (neuromuscular junction).
Brain problems include strokes, injuries, tumors, and degenerative disorders (such as multiple sclerosis, which also can affect the spinal cord and nerves). Spinal cord disorders include injury, bleeding, and tumors. Spinal nerve roots can be affected by a ruptured intervertebral disk, and peripheral nerves by injury or polyneuropathy. The neuromuscular junction can be affected by myasthenia gravis, drugs such as botulinum toxin Some Trade Names
injections, and certain poisons such as organophosphates (used in nerve gas and many insecticides).
Muscle disorders causing weakness include muscular dystrophy and polymyositis. The muscle weakness that commonly occurs following immobilization (in a cast or from prolonged bed rest) and in old age is due to a reduction in muscle mass (sarcopenia) and results from lack of use. The remaining muscle mass functions normally, but there is not an adequate amount.
Weakness may be limited to one extremity or part of an extremity, as is typically the case when a single nerve, joint, or muscle is affected, or diffuse, as occurs in widespread neurologic or muscular diseases.
Pain: People with pain in the muscles, ligaments, bones, or joints tend to consciously and unconsciously limit motion. This often gives the impression of weakness even though the nervous system and muscles are able to generate movement.
Evaluation and Treatment
Doctors can often diagnose weakness based on the person’s symptoms and the results of the physical examination. Doctors first try to determine whether the person can contract the muscles normally. If the person can contract the muscles normally but has trouble moving a joint, the doctor tries to move the joint for the person while the person relaxes (passive motion). If motion is painful, inflammation may be the problem. If passive motion causes little pain but is blocked, joint contracture (for example, due to scar tissue) may be the problem.
If passive motion is neither painful nor blocked, the person is giving full effort, and there is no sign of Parkinson’s disease or other neurologic disorder causing difficulty initiating movement, then true muscle weakness is likely. The cause of true muscle weakness can often be determined by noting the person’s symptoms, which muscles are affected, whether muscles have shrunk, and muscle tone and by testing the person’s reflexes with a reflex hammer. For example, if weakness affects mainly the large muscles such as the hips, thighs, and shoulders, the cause may be a disorder producing widespread damage to muscles. If weakness affects mainly the eye muscles (causing double vision), the cause may be a disorder of the neuromuscular junction. If weakness affects mainly the fingers, hands, and feet, particularly if there is loss of sensation, the cause may be a disorder that damages many nerves (polyneuropathy). The nerves to the fingers, hands, and feet are the body’s longest and thus the most vulnerable peripheral nerves. If muscles have shrunk, the disorder causing the problem has been present for months or years. If the person’s reflexes are decreased or slow, the cause may be nerve damage. If reflexes are increased or more rapid than expected, the cause may be spinal cord or brain damage. The doctor checks muscle tone by testing passive movement. Muscle tone may be decreased when weakness results from a peripheral nerve disorder. Muscle tone may be increased when weakness results from a spinal cord or brain disorder.
If the cause is still not clear, other tests can help. Disorders of the brain or spinal cord are diagnosed using neuroimaging tests such as CT or MRI. To differentiate between weakness caused by damage to the peripheral nerves, muscles, and neuromuscular junction, tests such as electromyography and nerve conduction velocity (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Electromyography and Nerve Conduction Studies) usually help. Certain other disorders (for example, low blood levels of potassium or vitamin D Some Trade Names
) are diagnosed with blood tests.