Page 48 - ASOP ROT Study Guide

3 . 4 . 4 Extensors
The hamstring muscles occupy the posterior compartment of the thigh. The hamstrings consist of
three muscles which are, specified from medial to lateral in the midthigh, the semimembranosus,
the semitendinosus, and the biceps femoris. The biceps femoris (Latin: two headed muscle of the
thigh) consists of a long head with origin at the ischial tuberosity and a short head with origin from
the distal posterior femoral diaphysis.
The common site of insertion is the fibular head. The other hamstring muscles along with the long
head of the biceps femoris originate from closely placed sites on the posterior/inferior surface of
the ischial tuberosity. The semimembranosus and the semitendinosus insert on the proximal
medial tibia.
The hamstrings "primary" function is NOT knee flexion. In walking or running, for example, the
primary function of the hamstring is to decelerate the lower leg in the sagittal plane. Positionally,
knee flexion in walking/running occurs as a result of hip flexion and plantarflexion, again
positionally.

www.med.wayne.edu/diagradiology/The%20CT%20Anatomy%20Tutor/Hamstrings.html