Psoas vs. Iliopsoas — What's the Difference?

The psoas major, often simply referred to as the psoas, is a deep-seated muscle that extends from the lumbar vertebrae to the femur. It plays a crucial role in flexing the hip joint and stabilizing the lower back. On the other hand, the iliopsoas refers to the combined group of the psoas major and the iliacus muscles. These two muscles work in concert to perform similar functions, but the iliacus originates from the iliac fossa of the pelvis, adding an extra layer of support for hip flexion and pelvic stability.

The psoas is known for its influence on posture and lower back health, as it helps maintain the spine's curvature. Whereas, the iliopsoas, due to the addition of the iliacus muscle, not only assists in maintaining posture but also has a more significant impact on hip movement, particularly in actions that require lifting the knee towards the chest.

In terms of anatomy, the psoas originates from the lumbar vertebrae and inserts into the lesser trochanter of the femur. Meanwhile, the iliopsoas, being a combination, includes the psoas major's origin and insertion points as well as those of the iliacus, which originates in the iliac fossa and joins the psoas major to insert into the lesser trochanter.

Issues related to the psoas muscle can lead to lower back pain, a common complaint among many people. The iliopsoas group, by extension, when tight or imbalanced, can contribute to a range of issues from lower back pain to hip and pelvic discomfort, underscoring the interconnected nature of these muscles and their functions.

Training and stretching the psoas muscle involve exercises that focus on the lower back and hips. However, targeting the iliopsoas requires a more holistic approach, incorporating movements that engage both the hip and the pelvic regions, reflecting the comprehensive function of the iliopsoas muscle group in body mechanics.