Gluteus Minimus
| |
| Gluteus Minimus | |
|---|---|
| Muscle Type | |
| Origin | From the area between the anterior gluteal line and inferior gluteal line on the gluteal surface of the ilium, beneath the gluteus medius. |
| Insertion | Greater trochanter of the femur (anterior facet) |
| Action | Works in concert with gluteus medius to abduct the hip and prevent adduction; contributes to medial rotation of the thigh. |
| Synergists | Gluteus Medius, Tensor Fasciae Latae, Gluteus Maximus |
| Antagonists | Lateral Rotator Group |
| Spinal innervation | L4, L5, S1 |
| Peripheral Innervation | Superior gluteal nerve |
| Vasculature | Superior gluteal artery |
The gluteus minimus is the smallest and deepest of the trio of gluteal muscles, situated immediately beneath the gluteus medius. It is a fan-shaped muscle that functions synergistically with the gluteus medius to abduct the hip and stabilize the pelvis. The gluteus minimus also contributes to internal rotation of the thigh. Its importance is often noted in the context of lateral hip stability and gait.
Structure
The gluteus minimus is a small, triangular muscle and represents the deep layer of the gluteal region’s abductors. It has a multipennate fiber orientation, which, due to its intimate relation to the hip joint capsule, sometimes leads it to be considered the “deltoid of the hip,” acting in concert with the gluteus medius.
Origin
It originates from the external surface of the ilium, in the area between the anterior and inferior gluteal lines on the ilium’s wing. This origin is inferior to that of the gluteus medius. The muscle fibers fan out from this origin, covering the bone just above.
Insertion
The gluteus minimus inserts into the anterior facet of the greater trochanter of the femur, blending with the capsule of the hip joint (sometimes sending fibers to reinforce the joint capsule). This attachment helps prevent impingement during hip movements. The insertion is essentially at the lateral aspect of the hip, providing leverage for abduction and rotation.
Action
Functionally, the gluteus minimus abducts the hip and works with the gluteus medius to stabilize the pelvis during single-leg stance. It also contributes to medial (internal) rotation of the thigh; when the hip is extended, its anterior positioning allows it to rotate the femur inward. During walking, as the foot lifts off the ground, the gluteus minimus on the stance side contracts to keep the pelvis level, preventing a drop on the swing side. Together, these muscles ensure a smooth gait.
Synergists
The gluteus minimus works in concert with the gluteus medius; they are often considered a functional unit for hip abduction and pelvic stabilization. The tensor fasciae latae (TFL) is another synergist for abduction and internal rotation, particularly during hip flexion. The superior fibers of the gluteus maximus can assist in abduction when the hip is in extension. In internal rotation of the thigh, the gluteus medius and minimus act together.
Antagonists
The lateral rotator group of the hip (including the piriformis, obturator internus and externus, superior and inferior gemelli, and quadratus femoris) oppose the medial rotation function of the gluteus minimus. Additionally, the hip adductors oppose its abduction action. When the gluteus minimus is weak, the antagonistic hip adductors (e.g., adductor magnus) can cause an imbalance by pulling the thigh toward the midline.
Spinal Innervation
Like the gluteus medius, it receives innervation predominantly from the L4, L5, and S1 nerve roots via the superior gluteal nerve.
Peripheral Innervation
The gluteus minimus is innervated by the superior gluteal nerve (the same as the gluteus medius and tensor fasciae latae). The nerve reaches the gluteus minimus after passing under the gluteus medius. Isolated injury to the nerve branches supplying the gluteus minimus is rare; usually, if the nerve is affected, both the gluteus medius and minimus present with deficits.
Vasculature
The superior gluteal artery supplies blood to the gluteus minimus, coursing between the medius and minimus. There is an abundant anastomosis around the hip, so the minimus also receives contributions from a branch of the lateral circumflex femoral artery. This ensures robust blood flow, which is beneficial as the tendon of the gluteus minimus must withstand significant stress, similar to a rotator cuff tendon.
Clinical Application
Gluteal Tendinopathy: Gluteus minimus tendinopathy often coexists with gluteus medius tendinopathy in Greater Trochanteric Pain Syndrome (GTPS). Imaging (MRI/ultrasound) may show tendinosis or partial thickness tears of the minimus tendon at the anterior facet of the trochanter. Isolated gluteus minimus tears are less frequent but can cause anterolateral hip pain and weakness in abduction. Such tears might mimic hip joint pathology. Treatment parallels that of gluteus medius injuries – rest, physical therapy emphasizing hip abductor strengthening, and possibly corticosteroid or PRP injections for chronic tendinopathy. In refractory cases, endoscopic repair of the gluteus minimus tendon may be considered.
Injection Targets: In cases of Greater Trochanteric Pain Syndrome, a properly placed injection often targets the subgluteus medius bursa, which lies just superficial to the gluteus minimus insertion. By reducing inflammation in this area, pain from both minimus and medius tendinopathy can be alleviated. Care is taken during these injections to avoid needling too deeply and entering the hip joint capsule, although the gluteus minimus fibers and capsule are in close proximity.
Nerve Entrapment: The superior gluteal nerve runs between the medius and minimus; a rare but possible source of lateral hip pain is compression of this nerve (e.g., by gluteal fascial bands or due to hypertrophy). This is sometimes referred to as “Deep Gluteal Syndrome,” though that usually involves sciatic entrapment. If superior gluteal nerve entrapment occurs, both the gluteus medius and minimus may weaken. Nerve conduction studies can help differentiate this from L5 radiculopathy.
Surgical Note: During lateral approaches to the hip (such as in osteotomies or certain arthroplasties), the gluteus minimus may be partially detached from the trochanter to allow joint access. Proper repair of this detachment is crucial to avoid postoperative abductor weakness. Surgeons take care to preserve the integrity of the minimus tendon or to reattach it securely to prevent a chronic abductor deficit.
Functional: Weakness of the gluteus minimus (for example, following poliomyelitis affecting L5) contributes to a positive Trendelenburg sign and gait disturbance. Conversely, strong gluteus medius/minimus muscles are essential in athletes for lateral movements, single-leg landings, and maintaining proper form during running. In rehabilitation, targeted exercises like side-lying leg raises (hip abduction) or band walks are used to strengthen both the minimus and medius.
