Which sign is most commonly associated with septic arthritis in the knee?

• A. Chronic swelling
• B. Rapid onset of joint swelling with severe pain and fever
• C. Asymptomatic
• D. Gradual onset with mild pain

Answer: (B)

Septic arthritis presents as an acute, rapidly progressive joint infection, most often in the knee, with sudden swelling, severe pain, warmth, and fever. This abrupt, intense inflammatory response reflects purulent synovial infection and requires urgent evaluation and treatment to prevent joint damage. The other patterns—chronic swelling, asymptomatic joint, or gradual onset with mild pain—fit non-infectious conditions such as inflammatory or degenerative arthritis rather than an acute infection. Hence, the description of rapid onset with severe pain and fever best matches septic arthritis.