As a group, the hamstring muscles pull the thigh backward and and bend the leg at the knee. They also rotate the tibia on the femur. All three of them originate on a particular spot on the ischium called the ischial (
The symmetrical arrangement of the group is worth noting. On the medial side is semitendinosus (
sem-ee-ten-din-OH-sus)lying over semimembranosus (
sem-ee-mem-bran-OH-sus). On the lateral side is biceps femoris (
BYE-seps FEM-or-iss), whose long head lies over its short head. Thus there is a two-part group on either side.