Psoas major
Musculus psoas major
MuscularDeep musclesWhole bodyLeft and right
View left in 3D View right in 3D
- What it is
- Long spindle-shaped muscle beside the lumbar spine, from the sides of the T12–L5 vertebral bodies, their discs and transverse processes, running down along the pelvic brim and under the inguinal ligament to join iliacus on the lesser trochanter of the femur.
- Function
- The main flexor of the hip; also flexes the trunk on the thigh (sitting up) and bends the lumbar spine sideways.
- Size
- About 30 cm long and up to 5 cm thick at the lower lumbar spine.
- Clinical note
- A spinal abscess can track down its sheath to the groin; pain on hip extension ("psoas sign") suggests an inflamed retrocaecal appendix.