iliopsoasflexion

Iliopsoas flexion refers to the action produced by the iliopsoas muscle group in bending the hip joint, bringing the thigh toward the trunk. The iliopsoas is formed by two muscles, the psoas major and the iliacus, which join to insert on the lesser trochanter of the femur. The combination acts as the primary flexor of the hip in many activities and also contributes to pelvic and lumbar spine stabilization during movement.

Anatomy and innervation: The psoas major originates from the bodies and intervertebral discs of T12 to L5 and the transverse processes of the lumbar vertebrae. The iliacus originates from the iliac fossa and iliac crest (and to a lesser extent the ala of the sacrum). The two muscles converge into a common tendon that inserts on the lesser trochanter. The psoas major is innervated primarily by the anterior rami of L1–L3, while the iliacus is innervated by the femoral nerve (L2–L4). Blood supply typically comes from branches of the iliolumbar and femoral arteries.

Function and biomechanics: As the main hip flexor, the iliopsoas initiates flexion of the thigh at the hip joint when the leg is moving freely. It also assists in external rotation of the hip and helps stabilize the pelvis and lumbar spine, especially during standing and gait. When the trunk flexes toward the thigh with the leg fixed, the iliopsoas can act to raise the torso, reflecting its role in core mobility as well as hip movement.

Clinical relevance: Tightness, strain, or overuse of the iliopsoas can contribute to hip or lower back pain and limited hip flexion. Clinical assessment may include the Thomas test or palpation, and management typically involves stretching, strengthening, and addressing related posture or gait issues.