By Elizabeth A. Murray, Mount St. Joseph University
The muscles that act on the hip are specifically in the gluteal region. There are not only three relatively large muscles with gluteal in their name, but also a series of five smaller muscles in the deep gluteal region.
Gluteus Maximus
Gluteus maximus has a broad origin, along the outer ilium, the posterior aspect of the sacrum and coccyx, and the sacrotuberous ligament, which remember, connects the sacrum to the ischial tuberosity. The gluteus maximus inserts partly on the conveniently named gluteal tuberosity on the femur, as well as the iliotibial tract, often called the IT band, both of which we’ll talk more about in the next lesson.
The lateral part of gluteus maximus inserts into the iliotibial tract thickening, in addition to its insertion on the gluteal tuberosity of the femur.
Actions of the Gluteus Maximus
Due to its size, position, and fiber direction, the gluteus maximus has varied actions, depending on what part of it is being used. As a whole, gluteus maximus is the major extensor of the thigh, as when kicking the thigh back, but it also extends the trunk, like when we’re climbing stairs. That’s why fitness stair machines or simply taking the stairs at work or at home, strengthen the gluteus maximus.
Extending the trunk is the action of the gluteus maximus when we raise our torso after putting our foot on the next step up. That’s also the same action that allows us to stand up from being seated on a chair, raising the trunk by extending both hip joints with our gluteus maximus muscles—same with raising up during squat exercises.
Because its fibers are directed laterally, toward its insertion on the iliotibial tract and femur, gluteus maximus also helps laterally rotate the thigh at the hip joint—as when pointing your toes out away from the body. When used alone, the upper fibers can help the other gluteal muscles abduct the thigh, while the lower fibers can help the muscles of the medial thigh to adduct the thigh.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Gluteus Medius and Minimus
Deep to the lateral aspect of gluteus maximus are gluteus medius and gluteus minimus. Both of these are supplied by the superior gluteal nerve, which exits the pelvis above the piriformis muscle.
Compared to gluteus maximus, the gluteus medius is also more superiorly placed—which is why it can be seen peeking out from superior to gluteus maximus. Gluteus medius is also the primary target for a clinician to give an intramuscular injection into the buttock; the needle should be placed in the superolateral quadrant of the gluteal region, which might hit the upper corner of gluteus maximus, as well.
Both gluteus medius and gluteus minimus take origin on the outer surface of the ilium, from what are called its gluteal lines, and both insert on the greater trochanter of the femur.
Actions of the Gluteus Medius and Minimus
Gluteus medius and minimus have identical actions: Both help stabilize the hip joint when we’re standing, especially when we raise our opposite limb.
Both also perform abduction of the femur at the hip joint, as well as aid in medial rotation of the lower limb at the hip. When seen in lab, gluteus medius and minimus appear almost like a single muscle with a neurovascular plane passing between them.
The superior gluteal nerve, artery, and vein all dive between gluteus medius and gluteus minimus, serving gluteus medius from its deep side, but supplying gluteus minimus from its superficial side. After serving gluteus medius and minimus, the superior gluteal nerve continues laterally to meet the tensor of the fascia lata.
Other Hip Muscles in the Deep Gluteal Region
The five remaining muscles of the gluteal region are deep to the gluteus maximus.
Piriformis is a triangle-shaped muscle with its base taking origin off the anterior sacrum and slightly on the sacrotuberous ligament. The apex of its triangular shape is its insertion on the greater trochanter of the femur, which it reaches by traveling out of the pelvis through the greater sciatic foramen.
Piriformis can abduct the thigh, especially when the hip is flexed, but can also laterally rotate the hip. It is innervated by small segmental branches of the sacral plexus, which remember forms on the anterior surface of the sacrum from the braiding of ventral rami of L4 to S4.
Obturator internus originates on the deep side of the rim of the pelvis’s obturator foramen, as well as from the membrane that covers most of the foramen. The tendon of obturator internus leaves the pelvis through the lesser sciatic foramen, formed by the crossing of the sacrotuberous and sacrospinous ligaments.
The superior gemellus muscle flanks the superior edge of the tendon of obturator internus, and the inferior gemellus muscle flanks its inferior edge. Together, the three muscles insert into the medial aspect of the greater trochanter, near the intertrochanteric crest that runs posteriorly between the greater and lesser trochanters.
Separate Muscles
In the body, these three appear almost as one wide muscle with a single central tendon. Then later, more detailed dissections and electromyographic studies confirmed that the two gemelli—plural of gemellus, which means “little twin” in Latin—were actually separate muscles from obturator internus.
The superior gemellus originates off the ischial spine, and the inferior gemellus originates off the superior edge of the ischial tuberosity. They don’t pass through the lesser sciatic foramen; they originate on its lateral edge.
Inferior to the inferior gemellus is the quadratus femoris muscle. It originates on the lateral edge of the ischial tuberosity and inserts on the intertrochanteric crest. Together, all of these muscles—piriformis, superior gemellus, obturator internus, inferior gemellus, and quadratus femoris—all laterally rotate the hip joint and help stabilize it.
Common Questions about Muscles of the Hip
The muscles that act on the hip are specifically in the gluteal region. There are not only three relatively large muscles with gluteal in their name, but also a series of five smaller muscles in the deep gluteal region.
The gluteus maximus is the major extensor of the thigh, as when kicking the thigh back, but it also extends the trunk, like when we’re climbing stairs.
The five muscles of the deep gluteal region are piriformis, superior gemellus, obturator internus, inferior gemellus, followed by quadratus femoris.
