Muscle · Glutes

Quadratus femoris

Musculus quadratus femoris

A short, flat, genuinely quadrilateral muscle — the lowest of the deep rotators — running straight across from the outer edge of the sit bone to the back of the femur between the trochanters. Its fibres are horizontal, which makes it an efficient external rotator and, more importantly, a compressor: it pulls the femur toward the socket. It is the strongest of the short rotators and, with the obturators and gemelli, delivers what the founder's system calls femoral head stability.