Gluteus medius and minimus Muscles
Anatomy and supply
The gluteus medius and minimus muscles, also referred to as the small gluteal muscles, are part of the dorsal gluteal musculature. The gluteus medius muscle (see picture left) forms the middle layer whereas the gluteus minimus muscle (see picture below) belongs to the deeper layer, along with the rotators of the hip joint. Both are supplied by the superior gluteal nerve, a branch of the sacral plexus (L4-S1).
The gluteus minimus muscle originates between the anterior and inferior gluteal lines of the ilium. The gluteus medius muscle originates more cranially between the anterior and posterior gluteal lines of the ilium thus entirely covering the gluteal minimus muscle. Both muscles insert at the greater trochanter of the femur. Topographically their caudal parts are in close proximity to the piriformis muscle which runs from the sacrum to the greater trochanter as well.
The small gluteal muscles are the most powerful abductors and inward rotators of the hip joint. A contraction of the ventral fibers results in a flexion and inward rotation. The dorsal fibers perform an extension and outward rotation. Altogether they play an important role in the stabilization of the pelvis.
A peripheral injury of the superior gluteal nerve may lead to loss of motor function. The classical sign is the pelvis dropping to the healthy side when standing on one leg (Trendelenburg’s sign). In order to maintain the balance the patients compensatorily bend their upper body to the side of the stance leg. Furthermore they walk with conspicuous sideward movements (Duchenne gait, also “waddling gait”)
When performing an intramuscular injection in the gluteal region an injury of the sciatic nerve and superior gluteal nerve has to be avoided. Therefore a recommended site of injection is the gluteus medius muscle in the upper outer quadrant of the buttock (Hochstetter's technique).