A Case of Localized Tenosynovial Giant Cell Tumor in the Infrapatellar Fat Pad of the Knee

Localized giant cell tumor of the tendon sheath (GCTTS) usually occurs in extensor an tendon sheath of the fingers and toes. It has rarely been observed in the fat pad of the knee joint. We treated a case of a 2.5×3×4 cm mass arising from the infrapatellar fat pad, which presented with extension limitation and knee pain due to lateral femorotibial joint impingement. The tumor was successfully treated using arthroscopic excision with a motorized shaver. Histologic findings were diagnosed as localized GCTTS. Herein we report this case with a literature review.