Posterior hip musculature
The posterior hip musculature comprises a group of muscles extending from the pelvic bone to the femur. These muscles are important for the stabilization of the pelvis during constant mechanical stress that it suffers. Also, the posterior hip muscles produce a movements within the hip joint, such are abduction, adduction, outward rotation and retroversion.
The hip joint is prone to injuries, especially in older people, whether it is due to some degenerative processes such as osteoporosis, or various accidental and pathological fractures. Strong and trained posterior hip muscles reduce the risk from the mechanical injuries.
Posterior hip muscles |
Obturator externus muscle Obturator internus muscle Superior gemellus muscle Inferior gemellus muscle Piriformis muscle Quadratus femoris muscle |
Innervation | All supplied by direct branches of the sacral plexus, except the external obturator that is supplied by the obturator nerve (branch of the lumbar plexus) |
Overall function | Stabilization of the pelvis and outward rotation of the hip joint |
This article will discuss the anatomy and function of the posterior hip muscles.
Anatomy
Origins and insertion
During their course they cross the hip joint dorsally. At the femur they all insert either at or near the greater trochanter which is why they are also referred to as the pelvitrochanteric muscles.
Muscles
In detail they consist of:
- Piriformis muscle - It runs from the anterior side of the sacral bone (facies pelvica) to the apex of the greater trochanter.
Origins | Anterior (pelvis) surface of the sacrum (between the S2 and S4), Gluteal surface of ilium near posterior inferior iliac spine (and sacrotuberous ligament) |
Insertions | (Apex of) Greater trochanter of the femur |
Innervartion |
Nerve to piriformis (S1-S2) |
Function |
Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum |
- Obturator externus muscle - The origin or proximal attachment of this muscle is found at the anterior surface of the obturator membrane, and bony boundaries of the obturator foramen. It inserts at the trochchanteric fossa of the femur.
Origins |
Anterior surface of obturator membrane, Bony boundaries of obturator foramen |
Insertions |
Trochanteric fossa of femur |
Innervartion |
Obturator nerve (L3, L4) |
Function |
Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum |
- Obturator internus muscle - This muscles extends from ischiopubic ramus and posterior surface of the obturator membrane, to the medial surface of the greater trochanter of femur.
Origins |
Ischiopubic ramus, Posterior surface of obturator membrane |
Insertions |
Medial surface of greater trochanter of femur |
Innervartion |
Nerve to obturator internus (L5-S2) |
Function |
Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum |
- Superior and inferior gemelli muscles - The superior gemellus muscle originates from the ischiadic spine whereas the inferior gemellus muscle has its origin at the ischial tuberosity. Both insert at the trochanteric fossa.
Superior gemellus muscle |
Origins: Ischial spine Insertions: Medial surface of greater trochanter, (via tendon of obturator internus) Innervation: Nerve to obturator internus (L5-S2) Function: Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum |
Inferior gemellus muscle |
Origins: Ischial tuberosity Insertions: Medial surface of greater trochanter, (via tendon of obturator internus) Innervation: Nerve to obturator internus (L5-S2) Function: Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum |
- Quadratus femoris muscle - It runs from the ischial tuberosity to the intertrochanteric crest of the femur.
Origins | (Lateral border of) Ischial tuberosity |
Insertions | (Quadrate tubercle on) Intertrochanteric crest of femur |
Innervation |
Nerve to quadratus femoris (L4-S1) |
Function |
Hip joint: Thigh external rotation; Stabilizes head of femur in acetabulum |
Innervation
The posterior hip muscles are innervated by direct branches of the sacral plexus – with the exception of the external obturator muscle.
Function
The main tasks of the posterior hip muscles are the stabilization of the pelvis and the external/lateral rotation of the hip joint. In addition particular muscles may support further hip movements: abduction (piriformis musclemuscle, external obturator muscle, gemelli muscles), adduction (quadratus femoris muscle) and retroversion (piriformis muscle, internal obturator muscle, gemelli muscles).
Clinical notes
Common causes for the insufficiency of the posterior hip muscles are fractures of the greater trochanter (e.g. by falling on the side), femoral neck fractures (often associated with osteoporosis in elderly) and ruptures during the implantation of a total hip endoprosthesis.
Every type of elevated trochanter (e.g. in coxa vara or hip dysplasia) and leg length discrepancies may lead to a weakening in the long term. Symptoms include local pain, limping up to the inability to walk.
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