Anatomy

Origin

The semimembranosus muscle is the best name for the hamstring muscle due to its expansive membranous tendon attachment to the lateral attachment to the ischial tuberosity.

The sciatic nerve travels lateral to the muscle down the thigh, the proximal to distal until reaching the knee.

Insertion

Semimembranosus muscle insertion and anatomy of the knee are essential to understanding the function. The semimembranosus muscle can contribute to knee pain and stretch a tight hamstring muscle.

There are six insertional attachments for the semimembranosus tendon.

• Posterior medial aspect of the tibia (groove)
• Tibia deep to the medial collateral ligament
• Broad tendinous insertion on the oblique popliteal ligament
• Meniscal arm to the coronary ligament of the posterior horn of the medial meniscus
• Fascia like arm blending into the popliteus muscle

Nerve

The sciatic nerve, tibial division

Function

The semimembranosus is a hamstring muscle that crosses both the hip and knee joints and causes movement at both joints
Classic functions include:

• Extension of the Hip when the foot is fixed (closed chain)
• Internal rotation of thigh when the hip is fully extended
• Flexion of the knee and internal rotation of lower leg on the thigh
• Stabilizes hip when truck tilts forward past bodies center of gravity.

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