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functional anatomy BY CHRISTY CAEL THE PSOAS Psoas major and minor create a connection between the trunk and lower extremity. Originating on the lateral aspect of the lumbar vertebrae, they directly stabilize the lower spine when the body is upright. The fi bers of psoas converge at, and must bend around, the anterior edge of the pelvic girdle. The tendon of psoas inserts on the lesser trochanter of the femur next to the iliacus. Both the psoas and iliacus fl ex PSOAS Attachments • origin: T12–l5 vertebrae, transverse processes, lateral bodies, and corresponding intervertebral disks. • insertion: femur, lesser trochanter Actions • Flexes the hip • Externally rotates the hip Innervation • l1–4 • lumbar plexus the hip during activities like walking, running, and jumping. These hip fl exors tend to be well developed and strong, because of constant use in posture and daily activities. The psoas major, psoas minor, and iliacus are sometimes combined to form the iliopsoas group, because they share an insertion and perform the same actions, hip fl exion, and external rotation. The psoas muscle plays a unique role in posture. When the body is standing, the psoas, along with quadratus lumborum and the erector spinae group, tilts the pelvis forward. These muscles must oppose the forces of the abdominals and gluteals, which tilt the pelvis backward. Together, these muscle groups maintain alignment between the trunk and pelvis. connect with your colleagues on massageprofessionals.com 95