The psoas minor is a vestigial muscle present in only approximately 60 percent of people, a small spindle-shaped muscle anterior to the psoas major with no hip joint action. Its primary function may be tensioning the iliac fascia. When present it can be identified on imaging alongside the psoas major but has negligible clinical significance. Its inconstant presence means it cannot be relied upon as a surgical landmark unlike the consistent psoas major.
| Origin | Lateral surfaces of T12 and L1 vertebral bodies |
|---|---|
| Insertion | Iliopubic eminence and iliac fascia |
| Nerve Supply | Ventral ramus of L1 |
| Blood Supply | Lumbar arteries |
| Actions | Weak flexion of the lumbar spine; Tenses the iliac fascia |
|---|
When present, its weak lumbar flexion action is redundant given the much more powerful psoas major and rectus abdominis. Its fascial tensioning role, if any, is not clinically detectable.
Psoas minor is absent in approximately 40 percent of the population. Its presence or absence is occasionally relevant in anatomical descriptions for surgical approaches to the retroperitoneal space and lumbar spine. In some forensic anthropology contexts, the presence of a psoas minor bony insertion mark on the iliopubic ramus is used as an anatomical variant marker.
Not individually palpable as it is a deep retroperitoneal structure anterior to the psoas major and not distinguishable clinically from it.
Rare finding on imaging when the retroperitoneal space is investigated for other pathology, of no clinical consequence in isolation.
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