Localized Pigmented Villonodular Synovitis of the Bilateral Knee: A Case Report

INTRODUCTION: Localized pigmented villonodular synovitis (PVNS) is a rare and benign condition of synovial tissue proliferation that affects the joints, tendon sheaths, and bursae. This case report is the first to describe a patient with a diagnosis of localized PVNS of the knee after presentation with bilateral and simultaneous onset of associated knee pain. CASE REPORT: A 28-year-old Japanese woman presented to our hospital with a 1-year history of bilateral knee pain and right knee locking that started 1 month ago. Magnetic resonance imaging demonstrated a mass lesion in both the anterior compartment of the right knee and in the posterior compartments of the left knee. Arthroscopic resection of the lesions was performed, and the diagnosis of localized PVNS was made by pathological analysis. At the 6-month follow-up, no evidence of recurrence was noted. CONCLUSION: This case report describes localized PVNS of the bilateral knee, which is extremely rare. PVNS is a disease requiring surgical resection and should not be overlooked. It should be treated with the possibility of bilateral occurrence in mind.