CHAPTER 90
Symptoms and Diagnosis of Musculoskeletal Disorders
The musculoskeletal system comprises bones, muscles, joints, ligaments, tendons, and bursae. Any of these components can be injured by trauma or affected by a number of diseases. Different diagnostic tests are available to diagnose musculoskeletal disorders, but the most important element of diagnosis is the doctor’s examination.
Common symptoms of musculoskeletal disorders include pain, weakness, stiffness, joint noises, and decreased range of motion. Inflammation can cause pain, swelling, warmth, tenderness, impaired function, and sometimes redness. Inflammation can result from many different musculoskeletal disorders, including autoimmune disorders and infections. Inflammation affects a joint; fluid may accumulate inside the joint, causing swelling and decreased range of motion.
Symptoms
PAIN
Pain is the chief symptom of most musculoskele-tal 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.
Causes
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 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 charley horse. 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 causes 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 such as acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), or, if pain is severe, opioids (see page 642). Depending on the cause, applying cold or heat or immobilizing the joint may help relieve musculoskeletal pain.
DIFFICULTY MOVING
A person may have difficulty moving all or part of the body.
Causes
Moving may be difficult because of disorders that restrict joint motion or that cause 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 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 studies (see page 636) usually help. Certain other disorders (for example, low blood levels of potassium or vitamin D) are diagnosed with blood tests.
For joints that are fixed, joint flexibility can be maximized by stretching exercises and physical therapy. If the joint’s range of motion is severely restricted by scar tissue, surgery may be necessary. The only way to relieve weakness is to treat the disorder causing it.
CLASSIFYING WEAKNESS
| UNDERLYING PROBLEM | EXAMPLE | DESCRIPTION |
| Muscle disease | Muscular dystrophies | A group of inherited muscle disorders that leads to muscle weakness of varying severity |
| Infections or inflammatory disorders (such as acute viral myositis or polymyositis) | Muscles tender or painful and weak | |
| Widespread muscle damage caused by use of a drug (drug-induced myopathy) | Myopathy due to corticosteroids, statins, lithium, alcohol, clofibrate, or colchicine | Weakness that usually begins at the hips and may spread to other muscles Sometimes no pain |
| Low blood levels of potassium | Hypokalemic myopathy (caused by certain disorders or use of diuretics) | Intermittent periods of weakness throughout the body |
| Abnormal levels of thyroid hormone | High levels of thyroid hormone (hyperthyroidism) or low levels of thyroid hormone (hypothyroidism) | High or low levels of thyroid hormone producing weakness that is usually more pronounced in the shoulders and hips than in the hands and feet |
| Low levels of vitamin D | Osteomalacia | Pain in the back, with weakness in the legs Rarely, pain throughout the body |
| Disease of the neuromuscular junction | Myasthenia gravis, curare toxicity, Eaton-Lambert syndrome, insecticide poisoning, botulism, or diphtheria | Weakness or paralysis affecting all or many muscles Sometimes affecting mainly eye muscles |
| Damage to a single nerve (mononeuropathy) | Diabetic neuropathy or local pressure | Weakness or paralysis of muscles and loss of sensation in the area served by the injured nerve |
| Damage to many nerves (polyneuropathy) | Diabetes, Guillain-Barré syndrome, folate deficiency, toxins, or drugs | Weakness or paralysis of muscles and loss of sensation in the areas served by the affected nerves |
| Spinal nerve root damage | Ruptured disk in the spine of the neck or lower back | Pain in the neck and weakness or numbness in an arm, low back pain shooting down the leg (sciatica), and leg weakness or numbness |
| Degeneration of nerve cell bodies in the spinal cord | Amyotrophic lateral sclerosis | Progressive loss of muscle bulk and strength, but no loss of sensation |
| Spinal cord damage | Trauma to the neck or back, spinal cord tumors, spinal stenosis, multiple sclerosis, transverse myelitis, or vitamin B12 deficiency | Weakness or paralysis of the arms and legs below the level of injury, progressive loss of sensation below the level of injury, and back pain Problems with bowel, bladder, and sexual function |
| Brain damage | Strokes, tumors, head trauma, multiple sclerosis, or infections | Weakness or paralysis of muscles in the area served by the injured part of the brain, often with other symptoms of brain damage |
| Psychologic problems | Depression or imagined symptoms or hysteria (conversion reaction) | Complaint of whole-body weakness or paralysis with no evidence of nerve damage |
JOINT STIFFNESS
Stiffness is the feeling that motion of a joint is limited or difficult. The feeling is not caused by weakness or reluctance to move the joint due to pain. Some people with stiffness are capable of moving the joint through its full range of motion. Joint stiffness usually occurs or is worse immediately after awakening or resting. Stiffness is common with arthritis. Morning stiffness commonly occurs with rheumatoid arthritis and other types of inflammatory arthritis in which stiffness typically occurs on arising and gradually lessens with activity only after an hour or two.
Doctors can sometimes diagnose the cause of stiffness by the person’s symptoms and the results of a physical examination. The person is examined to make sure that the problem is not pain with motion or weakness. Because arthritis is often the cause, blood tests (for example, rheumatoid factor and antinuclear antibodies) and x-rays may be done.
Stiffness is relieved by treating the disorder causing it. Stretching, physical therapy, and taking a hot shower on arising may improve the ability to perform activities that require flexibility.
JOINT NOISES
Joint noises, such as creaks and clicks, are common in many people, but they can also occur with specific problems of the joints. For example, the base of the knee cap may creak when it is damaged by osteoarthritis, and the jaw may click in a person who has temporomandibular joint disorder. Doctors ask about the person’s symptoms and perform an examination to determine whether a joint noise is a symptom of a certain disorder. Further evaluation and treatment are needed only if the evaluation suggests a significant joint problem. Joint noises themselves do not require treatment.
Diagnosis
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.
Physical Examination
A doctor looks for certain things during a physical examination depending on what disorder is suspected. When evaluating bones, if a fracture is suspected (see page 1952), the doctor may notice that the affected part (such as an arm or a leg) is abnormally shaped, suggesting that the segments of bone are out of alignment. A doctor may palpate the surfaces of the bones to detect any tenderness or abnormal shape, particularly if a fracture, a tumor, or a bone infection (osteomyelitis) is suspected. Compression fractures of the spine due to osteoporosis may be very painful at first, but no abnormal shape may be evident. Abnormal bumps in bones occasionally indicate a tumor. If osteomyelitis is suspected, a doctor or nurse checks for a fever.
When a person complains of muscle weakness, the doctor checks muscles for bulk and texture and for tenderness. Muscles are also checked for twitches and involuntary movements, which may indicate a nerve disease rather than a muscle disease. Doctors look for wasting away of muscle (atrophy), which can result from damage to the muscle or its nerves or from lack of use (disuse atrophy), as sometimes occurs with prolonged bed rest. Doctors also look for muscle enlargement (hypertrophy), which normally occurs with an 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 enlarge when normal muscle tissue is replaced by abnormal tissue (increasing the size but not the strength of the muscle), which occurs in amyloidosis and in certain inherited muscle disorders, such as Duchenne’s muscular dystrophy.
Doctors try to establish which (if any) muscles are weak and how weak they are. 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 their sagging, turning, or shaking. Downward drift of the arm with palms turning inward is a sign of weakness. Strength is tested by pushing or pulling while the doctor 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 or rising from a squatting position or getting up and down from a chair rapidly 10 times. The person is asked to look in all directions; if double vision develops, one or more eye muscles may be weak.
The doctor tests a joint’s range of motion by moving the limb around a joint while the person is completely relaxed (passive movement). The doctor also checks 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, doctors also tap the person’s muscle tendon with a rubber hammer to check reflexes (see page 633). 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. 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 Tests
Nerve conduction studies (see page 636) help determine whether the nerves supplying the muscles are functioning normally. Electromyography (see page 636), 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
X-rays (see page 2042) 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
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 and Magnetic Resonance Imaging
Computed tomography (CT—see page 2037) and magnetic resonance imaging (MRI—see page 2040) 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
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
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 (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
Arthroscopy is a procedure in which a small (the 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.