IlioPsoas Syndrome in Depth AKA: Hip Flexor Muscle Strain Common Signs & Symptoms PainSwellingStiffnessWeaknessInstabilityLocking IlioPsoas Syndrome Injury Explained Pain at the front of the hip may be due to a Hip Flexor muscle strain. The IlioPsoas muscle is most commonly affected. The IlioPsoas muscle is comprised of the Iliacus and Psoas muscles. The IlioPsoas muscle lies in front of the hip joint and sits quite deeply, below the surface of the skin. Its main job is to f