Muscle · Glutes

Gluteus medius

Musculus gluteus medius

A thick fan on the outer surface of the pelvis, running from the rim of the ilium down to the greater trochanter. Its famous action is lifting the leg out to the side, but that is not what it spends its day doing: every time you stand on one leg — which is half of every step you take — gluteus medius on the standing side contracts to stop the opposite side of the pelvis dropping. When it fails, the pelvis drops, the thigh falls inward, and the knee follows it into valgus. That single chain is why the founder's system links weak gluteus medius to knee pain, to running and gait problems, and to poor single-leg stability, and why it sits in the WEAK column of the tight/weak chart.