The gluteus maximus muscle is the strongest muscle in the body and covers a large part of the buttock. It connects the ilium, sacrum, and coccyx to the femur by tissues of the thigh and acts to extend the thigh. The gluteus maximus causes the leg to straighten at the hip when a person walks, runs, or climbs. It is also used to raise the body from a sitting position. It partly covers the gluteus medius muscle, which lies over-top of the gluteus minimus.