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.
Multiple pathways can cause disruption of the normal joint milieu leading to acute joint complaints. These pathways include degeneration of articular cartilage (osteoarthritis), deposition of immune complexes (rheumatoid arthritis), crystal-induced inflammation (gout and pseudogout), seronegative spondyloarthropathies (ankylosing spondylitis and Reiter syndrome), and bacterial and viral invasion (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 as can help narrow the differential diagnosis (Table 180-1). Systemic lupus erythematosus may present with a migratory pattern of joint pain, while migratory pain is characteristic of the following infectious etiologies: gonococcal arthritis, acute rheumatic fever, Lyme disease, and viral arthritis.
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.
Table 180-1 Classification of Arthritis by Number of Affected Joints |Favorite Table|Download (.pdf)
Table 180-1 Classification of Arthritis by Number of Affected Joints
|Number of Joints||Differential Considerations|
|1 = Monoarthritis||Trauma-induced arthritis|
|Nongonococcal septic arthritis|
|Gonococcal septic arthritis|
|Crystal-induced (gout, pseudogout)|
|2 to 3 = Oligoarthritis||Lyme disease|
|Reactive arthritis (Reiter syndrome)|
|>3 = Polyarthritis||Rheumatoid arthritis|
|Systemic lupus erythematosus|
|Serum sickness–like reactions|
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 a 90% sensitivity, the serum white blood cell count and erythrocyte sedimentation rate lack the sensitivity and specificity to be reliable discriminators in disorders of the joints and bursae. Adults with risks for sexually transmitted disease and migratory symptoms and or tenosynovitis should be evaluated for gonococcal arthritis.
Table 180-2 Examination of Synovial Fluid |Favorite Table|Download (.pdf)
Table 180-2 Examination of Synovial Fluid
|WBC/μL||<200||<200 to 2000||200 to 50 000||>50 000|