Some musculoskeletal disorders affect primarily the joints, causing arthritis. Others affect primarily the bones (eg, fractures, Paget disease of bone, tumors), muscles or other extra-articular soft tissues (eg, polymyalgia rheumatica, myositis), or periarticular soft tissues (eg, bursitis, tendinitis, sprain). Arthritis has myriad possible causes, including infection, autoimmune disorders, crystal-induced inflammation, and minimally inflammatory cartilage and bone disorders (eg, osteoarthritis). Arthritis may affect single joints ( monoarthritis) or multiple joints ( polyarthritis) in a symmetric or asymmetric manner, with or without involving the spine.
Baker cysts are enlarged bursae in the popliteal fossa. They are filled with synovial fluid and usually communicate with the adjacent joint space. Symptoms include pain, swelling behind the knee, and knee stiffness and decreased range of motion. Diagnosis is usually clinical; however, ultrasonography or magnetic resonance imaging may be needed if clinical findings are inconclusive. If symptomatic, treatment includes nonsteroidal anti-inflammatory drugs (NSAIDs) and, sometimes, arthrocentesis, corticosteroid injection, or surgical removal of the cyst.
Most foot problems result from anatomic disorders or abnormal function of articular or extra-articular structures (see figure Bones of the foot). Less commonly, foot problems reflect a systemic disorder (see table ).
Common hand disorders include a variety of deformities, ganglia, infections, Kienböck disease, nerve compression syndromes, noninfectious tenosynovitis, and osteoarthritis. (See also complex regional pain syndrome [reflex sympathetic dystrophy] and hand injuries.)
Aspiration of the olecranon bursa is done for diagnostic purposes (eg, to diagnose septic bursitis, gout). Injection of corticosteroids into the olecranon bursa is typically avoided but may be done selectively (eg, in patients with recurrent and painful, large effusions).
Immunoglobulin G4-related disease (IgG4-RD) is a chronic immune-mediated fibroinflammatory disorder that often manifests with tumor-like masses and/or painless enlargement of multiple organs. Serum IgG4 level is often but not always elevated. Symptoms depend on which organs are affected. Diagnosis generally requires biopsy. Treatment is with corticosteroids and sometimes rituximab.
Acute infectious (septic) arthritis is a joint infection that evolves over hours or days. The infection resides in synovial or periarticular tissues and is usually bacterial—in younger adults, frequently Neisseria gonorrhoeae. However, nongonococcal bacterial infections can also occur and can rapidly destroy joint structures. Symptoms include rapid onset of pain, effusion, and restriction of both active and passive range of motion, usually within a single joint. Diagnosis requires synovial fluid analysis and culture. Treatment is IV antibiotics and drainage of pus from joints.
Neurogenic arthropathy is a rapidly destructive arthropathy due to impaired pain perception and position sense, which can result from various underlying disorders, most commonly diabetes and stroke. Common manifestations include joint swelling, effusion, deformity, and instability. Pain may be disproportionately mild due to the underlying neuropathy. Diagnosis requires x-ray confirmation. Treatment consists of external or sometimes surgical joint stabilization to slow disease progression and reduce pain.
Neck pain and back pain are among the most common reasons for physician visits. This discussion covers neck pain involving the posterior neck (not pain limited to the anterior neck) and low back pain, but it does not cover most major traumatic injuries (eg, fractures, dislocations, subluxations).
Osteonecrosis is a focal infarct of bone that may be caused by specific etiologic factors or may be idiopathic. It can cause pain, limitation of motion, joint collapse, and secondary osteoarthritis. Diagnosis is by x-rays and MRI. In early stages, surgical procedures may slow or prevent progression. In later stages, joint replacement may be required for relief of pain and maintenance of function.
Osteoporosis is a progressive metabolic bone disease that decreases bone mineral density (bone mass per unit volume), with deterioration of bone structure. Skeletal weakness leads to fractures with minor or inapparent trauma, particularly in the thoracic and lumbar spine, wrist, and hip (called fragility fractures). Diagnosis is by dual-energy x-ray absorptiometry (DXA scan) or by confirmation of a fragility fracture. Prevention and treatment involve risk factor modification, calcium and vitamin D supplements, exercises to maximize bone and muscle strength, improve balance, and minimize the risk of falls, and drug therapy to preserve bone mass or stimulate new bone formation.
Paget disease of bone is a chronic disorder of the adult skeleton in which bone turnover is accelerated in localized areas. Normal matrix is replaced with softened and enlarged bone. The disease may be asymptomatic or cause gradual onset of bone pain or deformity. Diagnosis is by x-ray. Treatment includes symptomatic measures and often medications, usually bisphosphonates.
Patients may report "joint" pain regardless of whether the cause involves the joint itself or surrounding (periarticular) structures such as tendons and bursae; in both cases, pain in or around a single joint will be referred to as monoarticular pain.
Vasculitis is inflammation of blood vessels, often with ischemia, necrosis, and organ inflammation. Vasculitis can affect any blood vessel—arteries, arterioles, veins, venules, or capillaries. Clinical manifestations of specific vasculitic disorders are diverse and depend on the size and location of the involved vessels, the extent of the organ involvement, and the degree and pattern of extravascular inflammation.