Psoas Fascia

fascia musculi psoatis

The psoas fascia encloses the psoas major and minor muscles, forming the posterior wall of the retroperitoneal compartment. It attaches medially to the lumbar vertebral bodies and transverse processes, laterally blending with the quadratus lumborum fascia, and inferiorly continuing as the iliac fascia as the muscle crosses the pelvic brim.

Anatomical Data

Boundaries & Contents

Location	Posterior abdominal wall, covering psoas major
Boundaries	Medially: lumbar vertebral bodies, intervertebral discs and the fibrous arches over the lumbar vessels Above: thickened as the medial arcuate ligament Laterally: blends with the fascia over quadratus lumborum Below: continuous with the iliac fascia
Contents	Psoas major and psoas minor Lumbar plexus branches within or behind the muscle

Biomechanics

Function & Actions

Encloses psoas and guides the spread of a psoas abscess down into the groin and upper thigh.

Clinical Relevance

Clinical Notes

The psoas fascial compartment determines the spread of psoas abscess, which tracks within this fascia to present in the iliac fossa or femoral triangle. A psoas haematoma in anticoagulated patients or after lumbar surgery expands within the fascia, compressing the femoral nerve. The fascial compartment is the route for retroperitoneal haematoma propagation in lumbar artery injury.

Pathology

Common Injuries & Conditions

Psoas Compartment Haematoma

Retroperitoneal bleeding contained within the psoas fascia from anticoagulation or lumbar trauma, producing anterior thigh numbness from femoral nerve compression and a palpable flank mass.

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