Localized nodular synovitis of the knee: a case report.

A 25-year-old man with chronic swelling of the right knee had a mass that was eventually palpated in the suprapatellar pouch. Arthrotomy and biopsy revealed localized nodular synovitis. Since surgical excision of the mass the patient has been asymptomatic. While localized nodular synovitis generally appears as an internal derangement of the joint, this patient had signs and symptoms of chronic monoarthritis.