Psoas Major

Anterior views of spine and right hip. *Umbilicus. (Image by R. Dorn)

so-as

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Action
With the origin fixed:

• Flex the hip (coxal joint)
• May laterally rotate the hip (coxal joint)

With the insertion fixed:

• Flex the trunk toward the thigh
• Tilt the pelvis anteriorly

Unilaterally:

• Assist the laterally flex the lumbar spine

Origin

• Bodies and transverse processes of lumbar vertebrae

Insertion

• Lesser trochanter

Nerve

• Lumbar plexus L1, 2, 3​, 4

Location: Deep in abdomen, lateral to navel
BLMs: Bodies of lumbar vertebrae
Action: "Bring your knee toward your chest" or "flex your hip"