Psoas Minor Muscle Beneath the Skin

Description

Running along the posterior abdominal wall, the psoas minor appears as a slim fusiform muscle anterior to psoas major, arising from the bodies and intervertebral disc of T12 to L1 and tapering into a long tendon. Inferiorly, that tendon descends on the medial aspect of the iliopsoas compartment toward the pelvic brim, blending with the iliopubic eminence and pectineal line, often via the iliac fascia. Rectus abdominis and the linea alba occupy the anterior midline, while the oblique and transversus abdominis layers frame the lateral abdominal wall; posteriorly the lumbar vertebral column anchors the arrangement. Small muscle. Long tendon. Clinical relevance comes from what is present and what is often absent. Psoas minor is variably developed and may be unilateral or missing entirely, so identifying it correctly prevents mistaking its tendon for an anomalous band or fascial thickening during retroperitoneal exposure. For anterior approaches to the lumbar spine or when mobilizing the iliopsoas near the pelvic brim, this relationship to psoas major and the iliac fascia helps clarify where dissection planes naturally open, and where traction can transmit to the lumbar plexus within psoas major. In teaching, the plate suits gross anatomy labs and functional anatomy modules that compare psoas major, iliacus, and psoas minor in hip flexion versus trunk flexion mechanics, including discussion of postural low back pain where iliopsoas tightness is often implicated but psoas minor is not. It also supports surgical atlases and radiology correlation notes that explain why a thin psoas minor tendon may be subtle on CT or MRI and why its absence is a normal variant. Anatomical accuracy verified by SciePro's Medical Advisory Board.