Origin – Psoas major usually originates from two sections. The anterior bellies originate from the bodies and intervertebral discs of T12-L4. The posterior portion originates from the transverse processes of L1-L5. Nerve roots from the lumbar vertebrae pass between these sections.
Insertion – Psoas major blends with the fibers of iliacus, crosses the pubic bone and inserts on the lesser trochanter of the femur.
Function – Psoas major is primarily seen as a hip flexor but also flexes the trunk laterally. Its other functions can get complicated. For example, it is largely seen as contributing extending the lumbar spine and compressing the lower lumbar vertebrae, however, when the lumbar is in reverse curve, the upper sections can, paradoxically, flex the lumbar spine.
Tony Preston has a practice in Atlanta, Georgia where he sees clients.
He has written and taught about anatomy, trigger points and cranial therapies since the mid-90s.