Patients will report. Pain and difficulty when attempting to stand erect after extended periods of hip flexion after driving or readin seated at a desk or computer sleeping in a hip flexed or side lying fetal position the iliopsaos is the primary flexor of the thigh so pain is often experienced from the iliopsoas when the patient contracts the muscle to perform hip flexion or a sit up movements.
SI and LBP. Sacroiliac joint pain and low back pain psoas muscle can compress your l5-s1 disk with 500 newtons of pressure when it's in a spasm. Psoas will pull femur against the ilium and ilium against the sacrum to cause sacroiliac joint dysfunction and facet (spinal joint) related pain in the spine.