Diagnosis of Musculoskeletal Problems

A clinician can often diagnose a musculoskeletal disorder based on symptoms and the results of a physical examination. Laboratory tests, imaging tests, and other diagnostic procedures are sometimes necessary to help the clinician make or confirm a diagnosis.

Physical examination: When a person complains of muscle weakness, the clinician checks muscles for bulk, texture, and tenderness. Muscles are also checked for twitches and involuntary movements, which may indicate a nerve disease rather than a muscle disease. Clinicians look for wasting away of muscle (atrophy), which can result from damage to the muscle or its nerves or from lack of use, as sometimes occurs with prolonged bed rest. Clinicians look for muscle enlargement (hypertrophy), which normally occurs with exercise such as weight lifting. However, when a person is ill, hypertrophy may result from one muscle working harder to compensate for the weakness of another. Muscles can also become enlarged when normal muscle tissue is replaced by abnormal tissue (increasing the size but not the strength of the muscle), which occurs in certain inherited muscle disorders, such as Duchenne's muscular dystrophy.

Clinicians try to establish which (if any) muscles are weak as well as the degree of weakness involved. The muscles can be tested systematically, usually beginning with the face and neck, then the arms, and finally the legs. Normally, a person should be able to hold the arms extended, palms up, for one minute without them sagging, turning, or shaking. Downward drift of the arm with palms turning inward is one sign of weakness. Strength is tested by pushing or pulling while the clinician pushes and pulls in the opposite direction. Strength is also tested by having the person perform certain maneuvers, such as walking on the heels and tiptoes, rising from a squatting position, or getting up and down from a chair rapidly 10 times. To assess eye muscle strength, the person is asked to look in all directions; if double vision develops, one or more eye muscles may be weak.

The clinician tests a joint's range of motion by moving the limb around a joint while the person is completely relaxed (passive movement). The clinician will check muscle tone by testing passive movement. Resistance to such movement (passive resistance) may be decreased when the nerve leading to the muscle is damaged. Resistance to such movement may be increased when the spinal cord or brain is damaged. If a person is weak, clinicians also tap the person's muscle tendon with a rubber hammer to assess reflexes. Reflexes may be slower than expected when the nerve leading to the muscle is damaged. Reflexes may be more rapid than expected when the spinal cord or brain is damaged.

Laboratory tests: Laboratory tests are often helpful in making the diagnosis of a musculoskeletal disorder. A test called an erythrocyte sedimentation rate (ESR) test measures the rate at which red blood cells settle to the bottom of a test tube containing blood. The ESR is increased when inflammation is present. However, because inflammation occurs in so many conditions, the ESR alone does not establish a diagnosis. The level of creatine kinase (a normal muscle enzyme that leaks out and is released into the bloodstream when muscle is damaged) may also be tested. Levels of creatine kinase are increased when there is widespread and ongoing destruction of muscle. In rheumatoid arthritis, a blood test to identify rheumatoid factor or anti-cyclic citrullinated peptide (anti-CCP) antibody is helpful in making the diagnosis. In systemic lupus erythematosus (lupus), a blood test to identify autoimmune antibodies (antinuclear antibodies) is helpful in making the diagnosis.

Nerve tests: Nerve conduction studies help determine whether the nerves supplying the muscles are functioning normally. Nerve conduction studies, together with electromyography, help indicate whether there is a problem primarily in the muscles (such as myositis or muscular dystrophy); in the nervous system, which supplies the muscles (such as a stroke, spinal cord problem, or polyneuropathy); or with the neuromuscular junction (such as myasthenia gravis). Electromyography, often performed at the same time as nerve conduction studies, is a test in which electrical impulses in the muscles are recorded to help determine how well the impulses from the nerves are reaching the connection between nerves and muscles (neuromuscular junction).

X-rays: X-rays are most valuable for detecting abnormalities in bone and are taken to evaluate painful, deformed, or suspected abnormal areas of bone. Often, X-rays can help to diagnose fractures, tumors, injuries, infections, and deformities (such as congenital hip dysplasia). Also, X-rays may be helpful in showing changes that confirm a person has a certain kind of arthritis (for example, rheumatoid arthritis or osteoarthritis). X-rays do not show soft tissues such as muscles, bursae, ligaments, tendons, or nerves. To help determine whether the joint has been damaged by injury, a clinician may use an ordinary (non-stress) X-ray or one taken with the joint under stress (stress X-ray).

Arthrography is an X-ray procedure in which a dye is injected into a joint space to outline the structures, such as ligaments inside a joint. Arthrography can be used to view torn ligaments and fragmented cartilage in the joint.

Dual-energy X-ray absorptiometry (DEXA): The most accurate way to evaluate bone density, which is necessary when screening for or diagnosing osteoporosis, is with dual-energy X-ray absorptiometry (DEXA). In this test, low-dose X-rays are used to examine bone density at the lower spine, hip, wrist, or entire body. Measurements of bone density are very accurate at these sites. To help differentiate osteoporosis (the most common cause of an abnormal DEXA scan) from other bone disorders, doctors may need to consider the person's symptoms, medical conditions, medication use, and certain blood or urine test results as well as the DEXA results.

Computed tomography (CT) and magnetic resonance imaging (MRI): Computed tomography (CT) and magnetic resonance imaging (MRI) give much more detail than conventional X-rays. CT and MRI may be performed to determine the extent and exact location of musculoskeletal damage. These tests can also be used to detect fractures that are not visible on X-rays. MRI is especially valuable for imaging muscles, ligaments, and tendons. MRI can be used if the cause of pain is thought to be a severe soft-tissue problem (for example, rupture of a major ligament or tendon or damage to important structures inside the knee joint). The amount of time a person spends undergoing CT is much less than for MRI.

Bone scanning: Bone scanning is an imaging procedure that is occasionally used to diagnose a fracture, particularly if other tests, such as plain X-rays and CT or MRI, do not reveal the fracture. Bone scanning involves the use of a radioactive substance (technetium-99m-labeled pyrophosphate) that is absorbed by any healing bone. The technique can also be used when a bone infection or a metastasis (from a cancer elsewhere in the body) is suspected. The radioactive substance is given intravenously and is detected by a bone-scanning device, creating an image of the bone that can be viewed on a computer screen.

Joint aspiration: Joint aspiration is used to diagnose certain joint problems. A needle is inserted into a joint space and fluid (synovial fluid) is drawn out (aspirated) and examined under a microscope. A doctor can often make a diagnosis after analyzing the fluid. For example, a sample of synovial fluid may contain bacteria, which confirms a diagnosis of infection. Joint aspiration is usually performed in a doctor's office and is generally quick, easy, and relatively painless. The risk of joint infection is minimal.

Arthroscopy: Arthroscopy is a procedure in which a small (diameter of a pencil) fiber optic scope is inserted into a joint space, allowing the doctor to look inside the joint and to project the image onto a television screen. The skin incision is very small. A person receives local, spinal, or general anesthesia. During arthroscopy, doctors can take a piece of tissue for analysis (biopsy) and, if necessary, perform surgery to correct the condition. Disorders commonly found during arthroscopy include inflammation of the synovium lining a joint (synovitis); ligament, tendon, or cartilage tears; and loose pieces of bone or cartilage. Such conditions affect people with arthritis or previous joint injuries, as well as athletes. All of these conditions can be repaired or removed during arthroscopy. There is a very small risk of joint infection with this procedure.

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