Differential diagnosis of acute inflammatory oligoarthritis in adults

Acute inflammatory oligoarticular arthritis (oligoarthritis) is defined as arthritis affecting 2 to 4 joints. It may represent an evolving polyarthritis. The most common causes are the spondyloarthritides, including:

• reactive arthritis
• enteropathic arthritis
• psoriatic arthritis
• rheumatoid arthritis
• axial spondyloarthritis

Oligoarthritis may also present as:

• a condition that usually presents as a monoarthritis (eg gout, septic arthritis)
• an evolving polyarthritis; see causes in Differential diagnosis of acute inflammatory polyarthritis in adults.

Septic arthritis may present with an oligoarticular pattern in 10 to 20% of people; hence it is not excluded by finding 2 to 4 involved joints. Septic arthritis is a medical emergency that requires immediate referral to a hospital.