Major hip flexor, spine stabilizer.

Major muscle, flexes hip joint.

Infection causing abscess in muscle.

Small muscle, anterior pelvic tilt.

The psoas sign, also known as Cope's sign (or Cope's psoas test) or Obraztsova's sign, is a medical sign that indicates irritation to the iliopsoas group of hip flexors in the abdomen, and consequently indicates that the inflamed appendix is retrocaecal in orientation (as the iliopsoas muscle is retroperitoneal).

Major muscle for hip flexion.

Minor muscle, assists hip flexion.

The psoas minor muscle (or ; from ) is a long, slender skeletal muscle.

The psoas major (or ; from ) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis.