Overview
It is by far the largest of the gluteal muscles and gives the equine croup its bulk. Besides covering the wing of the ilium, it extends cranially over the longissimus lumborum, in a depression of that muscle's aponeurosis, as far as the cranial lumbar region. Its deep part is sometimes described as a separate muscle, the accessory gluteal (m. gluteus accessorius). In dissection it is partly covered by the superficial gluteal and biceps femoris.
Origin
Aponeurosis of the longissimus lumborum, gluteal surface of the ilium, coxal and sacral tuberosities, sacroiliac ligaments and broad sacrotuberous ligament.
Insertion
Greater trochanter of the femur (trochanter major). The tendon of its deep part glides over the trochanteric bursa before inserting.
Action
Extends the hip and abducts the pelvic limb. It is the main driver of propulsion, take-off, jumping and kicking, and takes part in rearing.
Innervation
Cranial gluteal nerve (n. gluteus cranialis).
Clinical relevance
- In exertional rhabdomyolysis ("tying-up") the gluteal and loin muscles become hard and painful; the horse sweats, is reluctant to move and blood creatine kinase rises.
- Trochanteric bursitis causes hind limb lameness with pain on pressure over the greater trochanter; it has been described mainly in Standardbreds.
- Intramuscular injections into the croup are not advised in the horse: if an abscess forms, it drains poorly from this deep muscle mass.