In this section, we’re going to cover the muscles of the gluteal region. This area contains muscles that perform abduction, extension and lateral rotation of lower limb at the hip. These muscles can broadly be split into mainly two groups:
1) Deep lateral rotators: quadratus femoris, piriformis, gemellus superior, gemellus inferior and obturator internus
2) Superficial abductors and extenders: gluteus minimus, gluteus medius and gluteus maximus. It also contains the tensor faciae latae, which acts on the knee joint.
The Superficial Muscles
Gluteus Maximus:
The largest of the gluteals, this is the most posterior muscle in the gluteal region and makes up most of the shape of the buttocks.
Attachments: It originates from the gluteal surface of the ilium, the sacrum and coccyx, sloping across the buttock at a 45 degree angle, then inserting into the iliotibial tract and gluteal tuberosity of the femur.
Actions: It is the main extensor of the thigh, and assists with lateral rotation. However, it is only used when force is required, such as running or climbing.
Innervation: Inferior gluteal nerve
Gluteus Medius:
This muscle lies deep to the gluteus maximum but above the gluteus minimus.
Attachments: Originates from the gluteal surface of the ilium and inserts into the lateral surface of the greater trochanter.
Actions: Abduction. It also prevents pelvic drop. With the hip flexed, the gluteus medius is a medial rotator.
Innervation: Superior gluteal nerve
Gluteus Minimus:
The gluteus minimus is the deepest and smallest of the gluteal muscles, and it is somewhat triangular shaped.
Attachments: It originates from the ilium and converges to form a tendon, inserting to the anterior side of the greater trochanter.
Actions: Abduction. It also prevents pelvic drop. With the hip flexed, the gluteus minimus is a stronger medial rotator than the gluteus medius
Innervation: Superior gluteal nerve
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Clinical Relevance: Damage to the Superior Gluteal Nerve
If the superior gluteal nerve is injured, the gluteus minimus and medius are paralysed. This can be spotted clinically by testing for pelvic drop. For example, if the superior gluteal nerve for the left leg is damaged, when the patient raises his right leg, the pelvis will drop on the right side. The patient may also walk with what is known as the gluteal gait – where the pelvis falls towards the unaffected leg on each step.
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The Deep Muscles
Piriformis
Attachments: This muscle originates from the sacrum’s anterior surface, then travels laterally and inferiorly, through the greater sciatic foramen, and behind the hip joint, to insert into the greater trochanter of the femur.
Actions: Lateral rotation and abduction
Innervation: Nerve to piriformis
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Clinical Relevance: Landmark of the Gluteal Region
The piriformis is a very important landmark in the gluteal region. As it travels through the greater sciatic foramen, it effectively divides it into an inferior and superior part.
This determines the name of the vessels and nerves in this region – the nerve and vessels that emerge superior to the piriformis are the superior gluteal nerve and superior gluteal vessels. Inferiorly, it is the same, and the sciatic nerve also travels inferiorly to the piriformis.
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Oburator Internus
As well have having its own individual functions, this muscle, along with the gemelli and quadratus femoris, pulls the head of the femur into the acetabulum, stablising the hip joint
Attachments: Originates from the pubis and ischium at the obturator foramen, the muscle travels through the lesser sciatic foramen, and attaches to the greater trochanter of the femur
Actions: Lateral rotation and abduction
Innervation: Nerve to obturator internus
The Gemelli – Superior and Inferior
These are two narrow, triangular muscles, that are seperated by the obturnator internus tendon.
Attachments: The superior gemellus muscle originates from the ischial spine, the inferior from the ischial tuberosity. They both attach to the greater trochanter of the femur
Actions: Lateral rotation and abduction
Innervation: The superior gemellus muscle is innervated by the nerve to obturator internus, the inferior gemellus is innervated by the nerve to quadratus femoris
Quadratus Femoris
This is a square shaped muscle, found below the gemelli and obturator internus
Attachments: The quadratus femoris originates from the lateral side of the ischial tuberosity, and attaches to the quadrate tuberosity on the intertrochanteric crest.
Actions: Laterally rotation
Innervation: Nerve to quadratus femoris
