Pigmented villonodular synovitis in the knee of a 5-year-old boy

Purpose of the study Case report of a five-year-old boy presenting with a p ainless swelling of the left knee with decreased range of motion. Method Joint aspiration: fluid rich in red blood cells. X-ray - CT-scan - MRI: pigmented villonodular synovitis suspected, Arthroscopy with synovectomy and biopsy confirmed diagnosis. Because of rem aining swelling one month after arthroscopy, intra-articular injection of t riamcinolone hexacetonide gave a good result which has been maintained afte r 2 years. Discussion Hypothesis on etiology and pathophysiology, differential diagnos is and treatment of Pigmented villonodular synovitis are discussed based on a study of the literature. Conclusion Pigmented villonodular synovitis is a rare condition in children . Association with other congenital disorders such as polyarticular localizat ions and family-history have been described. The diagnosis has to be proved by a biopsy. MRI seems to be the examination which gives the best information. Surgical treatment is indicated and consists of an arthroscopic synovectomy but which is often incomplete. A postoperative injection of triamcinolone hexacetonide may be the solution to avoid recurrence of Pigmented villonodular synovitis.