A doctor can often diagnose a musculoskeletal disorder based on the symptoms and on the results of a physical examination. Laboratory tests, imaging tests, or other diagnostic procedures are sometimes necessary to help the doctor make or confirm a diagnosis.
Laboratory tests are often helpful in making the diagnosis of a musculoskeletal disorder. For example, the erythrocyte sedimentation rate (ESR—a test that measures the rate at which red blood cells settle to the bottom of a test tube containing blood) 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 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.
Laboratory tests are also often useful to help monitor the progress of treatment. For example, the ESR can be particularly useful in helping to monitor the progress of treatment in rheumatoid arthritis or polymyalgia rheumatica.
Nerve conduction studies (see see Electromyography and Nerve Conduction Studies) help determine whether the nerves supplying the muscles are functioning normally. Electromyography (see see Electromyography and Nerve Conduction Studies), 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) and, from there, the muscles. 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). Nerve conduction studies are particularly useful in diagnosis of disorders of peripheral nerves, such as polyarteritis nodosa and ulnar nerve palsy.
X-rays (see see Plain 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, sometimes x-rays are 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 doctor 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 radiopaque dye is injected into a joint space to outline the structures, such as ligaments inside the joint. Arthrography can be used to view torn ligaments and fragmented cartilage in the joint. However, MRI is now generally used in preference to arthrography.
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—see Computed Tomography) and magnetic resonance imaging (MRI—see Magnetic Resonance Imaging) give much more detail than conventional x-rays and may be performed to determine the extent and exact location of 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). CT best images the bone; however, sometimes MRI is better than CT for imaging bone. The amount of time a person spends undergoing CT is much less than for MRI. MRI is more expensive than CT and, with the exception of when the open-sided units are used, many people feel claustrophobic inside the MRI unit.
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 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 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. Or, it may contain certain crystals, which confirms a diagnosis of gout (urate crystals) or pseudogout (see see Gout) (calcium crystals). Usually performed in the doctor's office, this procedure is generally quick, easy, and relatively painless. The risk of joint infection is minimal.
Arthroscopy is a procedure in which a small (diameter of a pencil) fiberoptic 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 the 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.
Recovery time after arthroscopic surgery is much faster than after traditional surgery. Most people do not need to stay overnight in the hospital.
Last full review/revision September 2006 by Michael Jacewicz, MD