[Villonodular synovitis of the knee in a 5-year-old child. Apropos of a case].

PURPOSE OF THE STUDY: Case report of a five-year-old boy presenting with a painless 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 remaining swelling one month after arthroscopy, intra-articular injection of triamcinolone hexacetonide gave a good result which has been maintained after 2 years.

DISCUSSION: Hypothesis on etiology and pathophysiology, differential diagnosis 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 localizations 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.