Quadratus femoris

The quadratus femoris (also quadratus femoris muscle, latin: musculus quadratus femoris) is a flat, quadrilateral muscle of the posterior group of the pelvic girdle.

Origin

The quadratus femoris originates from the ischial tuberosity.

Insertion

The quadratus femoris passes laterally and inserts onto the intertrochanteric crest of the femur.

Action

The quadratus femoris muscle is responsible for external (lateral) rotation of the thigh and along with the pectineus and the inferior fibers of gluteus maximus also assist in the adduction of the thigh. 

Innervation

The quadratus femoris is innervated by the sciatic nerve arising from the sacral plexus.