Gluteus Medius
| |
| Gluteus Medius | |
|---|---|
| Muscle Type | |
| Origin | Gluteal surface of ilium, under gluteus Maximus. Three areas of origin: gluteal fossa, gluteal aponeurosis, and posterior inferior edge of the lip of the iliac crest. |
| Insertion | Greater trochanter of the femur. Three points of insertion: tendinous portion of the aponeurosis inserts onto the superolateral facet, the remainder inserts along an anteroinferior oblique line on the lateral facet. |
| Action | Abduction of the hip; preventing adduction of the hip. Medial/internal rotation and flexion of the hip (anterior fibers). Extension and Lateral/external rotation of the hip (posterior fibers) |
| Synergists | Gluteus Minimus, Tensor Fascia Lata, Gluteus Maximus |
| Antagonists | Hip Adductors |
| Spinal innervation | L4, L5, S1 |
| Peripheral Innervation | Superior Gluteal Nerve |
| Vasculature | superior gluteal artery |
The gluteus medius is a fan shaped muscle on the outer surface of the pelvis. Lying deep to the gluteus maximus, it is one of the primary abductors of the hip and a key stabilizer of the pelvis during gait. The gluteus medius is critical for maintaining pelvic level when standing on one leg (e.g., in the mid-stance phase of walking). Dysfunction of this muscle can lead to a characteristic hip drop known as Trendelenburg sign.
Structure
The gluteus medius is a thick, fan-shaped muscle of the lateral hip (gluteal region). It lies in the intermediate layer of the gluteal muscles, sandwiched between gluteus maximus (superficial) and gluteus minimus (deep). Its fibers converge from a broad origin to a narrower insertion, giving it a pennate-like structure well-suited for stabilizing the pelvis.
Origin
It arises from the outer (gluteal) surface of the ilium, specifically the area between the posterior and anterior gluteal lines, and from the iliac crest just lateral to the iliac tubercle. A portion of its fibers also originate from the strong gluteal aponeurosis covering its surface.
Insertion
The gluteus medius inserts onto the greater trochanter of the femur. The posterior part of the muscle attaches to the superoposterior facet of the greater trochanter, while the anterior fibers blend with the gluteus minimus tendon inserting into the lateral facet as a broad insertion across the trochanter ensures a stable abduction force.
Action
The primary action is hip abduction, moving the thigh away from the midline. More critically, during single-leg stance (walking or running), the gluteus medius of the supporting leg prevents pelvic drop on the opposite side, keeping the pelvis level. Additionally, the anterior fibers assist in medial rotation of the thigh, while the posterior fibers can aid slight external rotation when the hip is extended. Collectively, with gluteus minimus, itfor normal gait mechanics.
Synergists
The gluteus minimus and tensor fasciae latae work synergistically with gluteus medius for hip abduction and internal rotation. In stabilizing the pelvis, these muscles together counteract the torque of body weight. The superior fibers of Gluteus Maximus can assist abduction as well, particularly in hip extension.
Antagonists
The adductor muscle group (adductor longus, brevis, magnus, pectineus, and gracilis) are antagonists, as they pull the thigh toward the midline, opposing abduction. During stance, an unopposed hip adductor force (due to weak gluteus medius) leads to contralateral hip drop. The external rotators (when the hip is extended) can oppose the medius’ internal rotation function.
Spinal Innervation
Derived primarily from the L4, L5, S1 spinal segments, via contributions to the superior gluteal nerve.
Peripheral Innervation
Supplied by the Superior Gluteal Nerve (branch of the sacral plexus). This nerve exits the pelvis through the greater sciatic foramen above the piriformis and runs in the plane between gluteus medius and minimus. It innervates gluteus medius, minimus, and tensor fasciae latae. Injury to the superior gluteal nerve (for example, from intramuscular injections that are too medial/inferior in the buttock or during hip surgeries) causes the Trendelenburg gait, where the pelvis sags toward the unsupported side.
Vasculature
The superior gluteal artery provides the dominant blood supply. This artery branches off the internal iliac artery and accompanies the nerve between the medius and minimus. Additional minor contributions come from the trochanteric anastomosis (branches of lateral circumflex femoral artery). Venous drainage parallels the arteries, emptying into the superior gluteal vein.
Clinical Application
Gluteal Tendinopathy: Degenerative tears or chronic overload of the gluteus medius tendon at the greater trochanter cause gluteal tendinopathy, a major component of Greater Trochanteric Pain Syndrome (GTPS). Patients (often middle-aged women) experience lateral hip pain and tenderness over the trochanter. MRI can show tendinosis or partial tearing of gluteus medius/minimus rather than isolated bursitis. Conservative management (physiotherapy focusing on hip abductors) is first-line. Ultrasound-guided corticosteroid injections around the gluteus medius tendon or into the subgluteus medius bursa can provide short-term relief. A 2010 study showed 72% of patients had improved pain 1 month after such an injection. For recalcitrant cases, newer approaches like PRP (platelet-rich plasma) or autologous tenocyte injections are being explored.
Trendelenburg Sign: Weakness or paralysis of gluteus medius (due to superior gluteal nerve palsy or L5 radiculopathy) leads to the Trendelenburg sign, where the pelvis drops on the contralateral side when standing on the affected limb. To compensate, patients lurch their torso toward the weak side (gluteus medius lurch) to maintain balance. This gait deviation indicates the need for strengthening or surgical repair if a tendon tear is present.
Injection Landmark: In avoiding iatrogenic nerve injury, the safe area for buttock injections is the supero-lateral quadrant, which targets gluteus medius fibers. Proper technique avoids the superior gluteal nerve (which runs more medially) and sciatic nerve (more inferior), while still delivering medication into a well-vascularized muscle belly.
Surgical Considerations: The gluteus medius may be surgically detached (trochanteric osteotomy or tendon release) during certain hip surgeries (e.g., Hardinge approach for hip arthroplasty) to allow access to the joint, and then repaired. A robust gluteus medius is vital post-op for restoring gait; tears can result in chronic limp. Surgeons sometimes refer to the gluteus medius as the “rotator cuff of the hip” due to its tendency to degenerate and tear in a similar fashion to shoulder rotator cuff tendons.
