Psoas minor muscle

Origin and insertion

The psoas minor muscle originates from the lateral aspect of the bodies of the T12 and L1 vertebrae, as well as the intervertebral disc found between them.

The muscle then extends inferiorly and tapers into a long, flat tendon, which is often longer than the muscle belly.

The tendon inserts onto the pecten pubis (pectineal line of pubis) and the iliopubic eminence via a thickened band of fascia known as the iliopectineal arch.

Relations

The psoas minor muscle is located entirely on the anterior surface of the psoas major muscle and thus shares a lot of its anterior relations. The right psoas minor sits posterior to the inferior vena cava and is crossed by the most distal end of the ileum, while the left psoas minor is crossed by the colon.

Along its anteromedial border, the muscle is related to the sympathetic trunk and the aortic lymph nodes.

Innervation

The psoas minor muscle is innervated by the anterior ramus of the spinal nerve L1.

Blood supply

The vascular supply of the psoas minor muscle comes mainly from the lumbar arteries. However, it also receives some minor contributions from the blood supply network of the psoas major muscle. This may include branches of the iliolumbar, obturator, external iliac and femoral arteries.

Function

The psoas minor is a very weak muscle and its absence does not result in any reduced functionality of the body, thus its exact function is not entirely clear. However, it is suggested that it assists in trunk flexion, allowing an individual to bend forward at the lumbar spine.