The posterior thigh houses the powerful hamstring muscles running from the ischial tuberosity of the ischium to the proximal tibia's medial side and the lateral side of the proximal fibula. These muscles are powerful hip extensors and knee flexors, and all but one of these muscles receive their motor innervation from the tibial portion of the sciatic nerve.

The hamstrings help control the swing of the lower limb during the so-called "swing phase" of walking - toe-off to heel-strike. In this mode, they control the amount of hip flexion that occurs during this "swing phase" of walking by acting concentrically, resisting lengthening. Therefore, even as they are called hip extensors, they really are very active in limiting hip flexion. They certainly become active as hip extensors in more strenuous forms of exercise, such as running or climbing stairs.

The sciatic nerve, emerges from under the piriformis and descends on the posterior thigh between the long and short heads of the biceps femoris, lateral to the semimembranosus.

Slightly superior to the knee, the sciatic nerve splits into its two components: the common peroneal nerve, which wraps around the lateral side of the leg near the head of the fibula, innervating the anterior and lateral leg, and the tibial portion of the sciatic which continues in the popliteal fossa with the popliteal artery and vein innervating the posterior leg (calf) region.