||This article may be too technical for most readers to understand. (December 2013)|
Anterior hip muscles. The iliopsoas is not labeled but can be seen as the psoas major and the iliacus join inferiorly.
|Iliac fossa and lumbar spine|
|Lesser trochanter of femur|
|Medial femoral circumflex artery and iliolumbar artery|
|Branches from L2-L4|
|Actions||Flexion of hip|
|Gluteus maximus and the posterior compartment of thigh|
|Anatomical terms of muscle|
The term iliopsoas (ilio-so-as) refers to the combination of the psoas major and the iliacus at their inferior ends. These muscles are distinct in the abdomen, but usually indistinguishable in the thigh. As such, they are usually given the common name "iliopsoas" and are referred to as the "dorsal hip muscles" or "inner hip muscles". The psoas minor does not contribute to the iliopsoas muscle.
The psoas major unites with the iliacus at the level of the inguinal ligament and crosses the hip joint to insert on the lesser trochanter of the femur. The iliopsoas is involved in flexion and lateral rotation (supination) of the thigh. If the limb is fixed they involve in flexion of the trunk.
It is a composite muscle. The psoas major is innervated by direct branches of the anterior rami off the lumbar plexus at the levels of L2-L4, while the iliacus is innervated by the femoral nerve (which is composed of nerves from the anterior rami of L2-L4).
The iliopsoas is the strongest of the hip flexors (others are rectus femoris, sartorius, and tensor fasciae latae). The iliopsoas is important for standing, walking, and running. The iliacus and psoas major perform different actions when postural changes occur.
The iliopsoas muscle is covered by the iliac fascia, which begins as a strong tube-shaped psoas fascia, which surround the psoas major muscle as it passes under the medial arcuate ligament. Together with the iliac fascia, it continues down to the inguinal ligament where it forms the iliopectineal arch which separates the muscular and vascular lacunae.
It is, however, a typical posture muscle dominated by slow-twitch red type 1 fibers. Therefore, it is susceptible to pathological shortening or contracture, especially in older people with a sedentary lifestyle, and requires regular stretching to maintain normal length. Such shortening can lead to increased anterior pelvic tilt and lumbar lordosis (unilateral shortening), and limitation of hip extension (bilateral weakness).
- This article uses anatomical terminology; for an overview, see anatomical terminology.
- Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol 1: Locomotor system (5th ed.). Thieme. p. 234. ISBN 3-13-533305-1.
- Thieme Atlas of Anatomy. Thieme. 2006. pp. 422–423. ISBN 3131421010.
- Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol 1: Locomotor system (5th ed.). Thieme. p. 254. ISBN 3-13-533305-1.
- "Iliopsoas". Retrieved 1 September 2010.
- Muscles/Iliopsoas at exrx.net
- Cross section image: pelvis/pelvis-e12-15 - Plastination Laboratory at the Medical University of Vienna