TENDINOUS INSERTION OF SEMIMEMBRANOSUS MUSCLE INTO THE LATERAL MENISCUS

Forty-two cadaver knees were used for morphologic and MRI observations of the tendinous distal expansions of the semimembranosus m. and the posterior capsular structures of the knee. A tendinous branch of the s emimembranosus m. inserting into the posterior horn of the lateral men iscus was found in 43.2% of the knees dissected, besides five already known insertional branches; capsular, direct, anterior and inferior, a s well as the oblique popliteal ligament. The tendon had three morphol ogic types; thin, broad and round. All three types moved the lateral m eniscus posteriorly when pulled on. Thus, the semimembranosus m. may a lso have a protective function for the lateral meniscus as well as the already well established function of protecting the medial meniscus i n knee flexion. When a semimembranosus tendon attachment to the poster ior horn of the lateral meniscus is present, its normal insertion is d ifficult to differentiate from a lateral meniscus tear in MRI and this may cause misdiagnosis.