Gluteus maximus and powerful hip extension

Gluteus maximus is the largest and most superficial of the gluteal muscles, and it gives the buttock its shape. It arises from the back of the ilium (the upper bone of the pelvis), the sacrum and the coccyx. It attaches to the femur at the gluteal tuberosity (a rough ridge on the upper femur) and to the iliotibial tract (a thick band of connective tissue down the outer thigh).

Its main job is hip extension: moving the thigh backwards, or bringing the trunk upright over a fixed thigh. Because the muscle runs behind the hip joint, contraction pulls the thigh backwards. It is called on mainly when force is needed, such as rising from a seated position, climbing stairs or sprinting, although it also contributes during normal walking. It gives some help with lateral rotation (turning the thigh outwards) as well.

The inferior gluteal nerve supplies the muscle. A deep wound over the back of the hip can injure the muscle or its nerve, and it then becomes hard to stand up from sitting or to climb stairs.

Do not confuse it with gluteus medius and gluteus minimus. They lie deep to it, abduct the hip (move the thigh out to the side), turn the thigh inwards, and keep the pelvis level when one foot is off the ground. They are supplied by the superior gluteal nerve. So when hip extension is weak but abduction and medial rotation are normal, think of gluteus maximus.