Quadratus femoris muscle

The quadratus femoris is a flat, quadrilateral muscle, between the gemellus inferior and the upper margin of the adductor magnus; it is separated from the latter by the terminal branches of the medial femoral circumflex vessels.

It arises from the upper part of the external border of the tuberosity of the ischium, and is inserted into the upper part of the linea quadrata—that is, the line which extends vertically downward from the intertrochanteric crest.

A bursa is often found between the front of this muscle and the lesser trochanter. Sometimes absent.

The primary action of quadratus femoris is external or lateral rotation of the hip, it also acts to steady the femoral head in the acetabulum.