Pain is the most common symptom of most musculoskeletal disorders. Pain ranges from mild to severe and from acute and short-lived to chronic and of long duration and may be local or widespread (diffuse).
Musculoskeletal pain can be caused by disorders of bones, joints, muscles, tendons, ligaments, bursae, or a combination (see Introduction to the Biology of the Musculoskeletal System). Injuries are the most common cause of pain.
Muscle pain (known as myalgia) 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, loss of blood flow to the muscle, infection, or a tumor. Polymyalgia rheumatica is a disorder that causes severe pain and stiffness in the neck, shoulders, upper and lower back, and hips.
Tendon and ligament pain is often less intense than bone pain. It is often described as "sharp" and is worse when the affected tendon or ligament is stretched or moved and is usually relieved by rest. Common causes of tendon pain include tendinitis, tenosynovitis, lateral epicondylitis or medial epicondylitis, and tendon injuries. The most common cause of ligament pain is injury (sprains).
Bursae pain can be caused by trauma, overuse, gout, or infection. Bursae are small fluid-filled sacs that provide a protective cushion around joints. Usually, pain is worse with movement involving the bursa and is relieved by rest. The affected bursa may swell.
Joint pain (called arthralgia) may or may not be related to joint inflammation (called arthritis). Arthritis may cause swelling as well as pain. A wide variety of disorders can cause arthritis, including inflammatory arthritis (such as rheumatoid arthritis), osteoarthritis, infectious arthritis, gout and related disorders, autoimmune disorders (such as systemic lupus erythematosus) and vasculitic disorders (such as immunoglobulin A–associated vasculitis), osteonecrosis, and injuries affecting the part of a bone inside a joint. Arthritic pain can be new (acute, for example, when caused by infections, injuries, or gout), or longstanding (chronic, for example, when caused by rheumatoid arthritis or osteoarthritis). Pain resulting from arthritis is typically worse when the joint is moved but usually is present even when the joint is not being moved. Sometimes pain originating in structures near the joint, such as ligaments, tendons, and bursae, seems to be coming from the joint.
Fibromyalgia may cause pain in the muscles, tendons, or ligaments. The pain is usually felt or causes tenderness in multiple locations and may be difficult to describe precisely but is usually not coming from the joints. Affected people usually have other symptoms, such as fatigue and poor sleep.
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. It is usually accompanied by tingling, numbness, or both.
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 lungs, spleen, or gallbladder. Back pain may be caused by a kidney stone, abdominal aortic aneurysm, inflammation of the pancreas, or, in women, pelvic disorders. Arm pain may be caused by a heart attack (myocardial infarction).
In trying to establish the cause of joint pain, doctors first determine
How many and which joints are involved
Whether the central part of the skeleton (such as the spine and pelvis) is involved
Whether the joint pain is acute or chronic
What factors relieve or worsen the pain
Whether there are other symptoms affecting other organs (for example, rash, fever, or dry eyes)
Determining these factors gives important clues to what disorder is likely causing the pain. Doctors do a physical examination to help determine these factors and detect other important findings that could help determine the cause of the pain.
Sometimes, the type of pain suggests where the pain has originated. For example, pain that worsens with movement suggests a musculoskeletal disorder. Pain with muscle spasm suggests that pain is caused by a muscle disorder (sometimes a chronic spinal cord injury). The site of swelling or the location of tenderness when the doctor feels (palpates) the area (for example, a joint, ligament, or bursa) or passively moves a joint 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, physical examination findings, and often the results of laboratory tests and x-rays. For example, Lyme disease often causes joint pain with swelling and a bull's eye-like rash, and 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 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.
X-rays are primarily used to take images of bones, but 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).
Magnetic resonance imaging (MRI), unlike plain x-rays, 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; it may not be better than a standard x-ray in the evaluation of many painful conditions. MRI can detect fractures that are not visible on x-rays.
Computed tomography (CT) 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. A CT scan is useful if MRI cannot be done or is unavailable.
Other imaging tests include ultrasonography, arthrography (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), and bone scanning. These tests may help doctors diagnose certain conditions. Doctors may remove a sample of bone, the lining of the joint (synovium), or other tissues for examination under a microscope (biopsy).
Joint fluid testing is often done if the joint is swollen. Doctors extract the fluid from the joint by first sterilizing the area with an antiseptic solution and then numbing the skin with an anesthetic. Then a needle is inserted into the joint and joint fluid is withdrawn (a procedure called joint aspiration or arthrocentesis). This procedure causes little or no pain. The fluid is usually tested for, among other things, bacteria that can cause infection and is examined under a microscope for crystals that cause gout and related disorders.
Pain is usually best relieved by treating its cause. The doctor may recommend pain relievers (see Treatment of Pain) such as acetaminophen, 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.