This amazing muscle has a major influence on our movement and wellbeing. The Psoas (pronounced soh-as) is one of the largest and thickest muscles in the body consisting of the Psoas Major and the Psoas Minor. It is the only muscle to link the lumbar spine (lower back) to the legs. It attaches to the twelfth thoracic (rib) vertebra T12 and lumbar (lower back) vertebrae L1 – L5, to the head of the less trochanter of the femur (thigh bone). It happily works with the iliacus musc