The anterior horn of the medial meniscus is the site of most variations, but anomalies of the medial meniscus are extremely rare. From July 1990 through December 1994, the authors performed arthroscopy on 1068 symptomatic knee joints and incidentally found anomalous insertion of the anterior horn of the medial meniscus into the anterior cruciate ligament in eleven knees. They had another lesion(7 discoid lateral meniscus with or without tear, medial collateral ligament tear, Posterior cruciate ligament avulsion fracture). All but one discoid lateral menisci were reshaped, one had to be treated by total lateral meniscectomy, discoid medial meniscus also by reshaping, torn medial meniscus by partial meniscectomy, torn medial collateral ligament by repair and avulsion fracture of posterior cruciate ligament by arthroscopic pinmonths(average, 21.7 months) after surgery. The results were satisfactory except for 2 patients. One damaged his knee in a traffic accident and the other was treated by total meniscectomy of discoid lateral meniscus. It was concluded that this anomaly was not related to the patient's symptoms and mainly associated with discoid lateral meniscus.