Middle gluteal muscle

Musculus gluteus medius

Extends the hip and drives the limb back; it is the main muscle of the croup.

Where it runs from and to

A muscle is told apart from its neighbours by what it takes hold of at each end, which is also what decides what it does when it shortens.

Origin: The longissimus aponeurosis over the loins, the ilium's gluteal face, the sacrum and the sacrosciatic ligament.
Insertion: The femur's greater trochanter.
Action: Extends the hip and drives the limb back; it is the main muscle of the croup.
Nerve: Cranial gluteal nerve.

Written for Vetomica in its own words from the standard reference anatomy of the horse; the books it was checked against are listed below.