The Gluteus is comprise of three smaller muscles, the Gluteus Maximus, the Gluteus Medius and the Gluteus Minimus. The gluteus is our rear end, and is the biggest muscle group on the body.
The gluteus is mainly responsible for allowing your legs to rotate at the hip, turing the thighbones outward. This is called an "external rotator." Because there are more muscles that act as "inward rotators" - muscles that pull the thighs inward - than external rotators, the lack of proper exercise will cause the outward rotators to weaken, in turn causing the thighs to point inwards. This results in several problems, including pigeon-toes, and high arches in feet. It can also cause undo strain on the knees, and tightening of the hamstrings.