Posterior cutaneous nerve of thigh
The posterior cutaneous nerve of the thigh (also called the posterior femoral cutaneous nerve) is a sensory nerve in the thigh. It supplies the skin of the posterior surface of the thigh, leg, buttock, and also the perineum. Structure. The posterior cutaneous nerve of the thigh is a nerve from the sacral plexus. It arises partly from the dorsal divisions of the S1 and S2, and from the ventral divisions of S2 and S3 sacral spinal nerves. It leaves the pelvis through the greater sciatic foramen below the piriformis muscle. It then descends beneath the  gluteus maximus muscle with the inferior gluteal artery, and runs down the back of the thigh beneath the fascia lata. It runs over the long head of the biceps femoris to the back of the knee. It then pierces the deep fascia, and accompanies the small saphenous vein to about the middle of the back of the leg. Its terminal branches communicate with the sural nerve. Branches. Its branches are all cutaneous, and are distributed to the gluteal region, the perineum, and the back of the thigh and leg. Function. The posterior cutaneous nerve of the thigh supplies the posterior  surface of the thigh, the leg, and the gluteal region, as well as the perineum. Clinical significance. The posterior cutaneous nerve of the thigh may be involved in pain in the posterior thigh.