Psoas impingement syndrome in hip osteoarthritis.

The degenerative processes underlying osteoarthritis of the hip produce both anatomical and biomechanical changes in and around the involved joint. A good understanding of hip anatomy and the forces crossing the hip joint is essential to understand both hip pathology and current treatment techniques. Total hip arthroplasty (THA) has become a mainstay of treatment for advanced osteoarthritis of the hip. Several factors contribute to post-operative hip pain in THA patients. Iliopsoas impingement on the prosthetic cup after total hip replacement is one of the causes of pain following hip surgery, often due to an anterior overlap of the implant with respect to the acetabulum. The anatomic shape of the anterior acetabular ridge, which may be straight or curved, influences this overlap. In this paper we present a case illustrating a psoas impingement-like syndrome in a patient with severe hip osteoarthritis who has not undergone hip replacement surgery. We discuss the compensatory strategies employed by the patient to reduce pain and prevent falls, and show CT scan images depicting the underlying anatomic pathology.