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Acute disorders of the joints and bursae are common emergency conditions that involve a wide spectrum of ages, acuities, and etiologies. Mismanagement of certain pathologic entities can lead to significant morbidity for the patient.
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Multiple pathways can cause disruption of the normal joint milieu leading to acute joint complaints. These pathways include degeneration of articular cartilage with osteoarthritis, deposition of immune complexes as in rheumatoid arthritis, crystal-induced inflammation in gout and pseudogout, seronegative spondyloarthropathies such as ankylosing spondylitis and Reiter's syndrome, and the bacterial or viral invasion of septic arthritis. These pathologic events invariably lead to pain, the most common complaint of patients with a joint problem. Important historical factors to elicit include a determination of previous joint or bursal disease, presence of constitutional symptoms and whether the pain is acute, chronic, or acute on chronic. Determining the number and distribution of joints affected can help narrow the differential diagnosis (Table 180-1). A migratory pattern of joint pain can be seen with systemic lupus erythematosus and in many infectious etiologies such as gonococcal arthritis, acute rheumatic fever, Lyme disease, and viral arthritis.
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On physical examination, arthritis should be distinguished from more focal periarticular inflammatory processes such as cellulitis, bursitis, and tendonitis. True arthritis produces joint pain exacerbated by active and passive motions. Skin erythema and warmth overlying a joint should be noted, although it is nonspecific regarding etiology of joint pathology.
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DIAGNOSIS AND DIFFERENTIAL
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With the exception of recent joint surgery or cellulitis overlying a prosthetic knee or hip, history, physical examination, and routine blood tests do not distinguish acute septic arthritis from other forms of arthritis. Clinicians who suspect septic arthritis based on the patient's presentation should perform arthrocentesis. Synovial fluid should be sent for culture, Gram stain, cell count, and crystal evaluation (Table 180-2). Except in pediatric septic arthritis, where the erythrocyte sedimentation rate has been shown to have 90% sensitivity, the serum white blood cell count and erythrocyte ...