290 THE JOURNAL OF BONE AND JOINT SURGERY

The occurrence of endometriosis in areas other than the abdomen and pelvis is uncommon, and in the extremities it is rare. The case of a patient who had endometriosis in the body of the biceps femoris and a review of the literature on lesions in the extremities are presented. Photograph of the mass that was fund within the body of the biceps femoris. A reddish tan or rust-colored central area is surrounded by fibrosed skeletal muscle. The mass measured four b three by two centimeters and was firm.