Psoas Major Muscle

Psoas Major Muscle

The psoas major (/ˈsoʊ.əz/) is a long fusiform muscle located on the side of the lumbar region of the vertebral column and brim of the lesser pelvis. It joins the iliacus muscle to form the iliopsoas. In less than 50 percent of human subjects, the psoas major is accompanied by the psoas minor. In mice, it is mostly a fast-twitching, type II muscle, while in human it combines slow and fast-twitching fibers.