Ischiofemoral impingement syndrome (IFI) is an underrecognized form of atypical, extra-articular hip impingement defined by hip pain related to narrowing of the space between the ischial tuberosity and the femur. The etiology of IFI is multifactorial and potential sources of ischiofemoral engagement include anatomic variants of the proximal femur or pelvis, functional disorders as hip instability, pelvic/spinal instability, or abductor/adductor imbalance, ischial tuberosity enthesopathies, trauma/overuse or extreme hip motion, iatrogenic conditions, tumors and other pathologies. Magnetic resonance imaging (MRI) is the diagnostic procedure of choice for assessing IFI and may substantially influence patient management. The injection test of the ischiofemoral space (IFS) has both a diagnostic and therapeutic function. Endoscopic decompression of the IFS appears useful in improving function and diminishing hip pain in patients with IFI but conservative treatment is always the first step in the treatment algorithm. Because of the ever-increasing use of advanced MRI techniques, the frequent response to conservative treatment, and the excellent outcomes of new endoscopic treatment, radiologists must be aware of factors that predispose or cause IFI. In addition, focused treatment in these conditions is often more important than in secondary impingement. In this article, we briefly describe the anatomy of the IFS, review the clinical examination and symptoms, assess the diagnostic imaging criteria and pathophysiological mechanisms, and develop an understandable classification of IFI, with particular focus on its etiology, predisposing factors, and associated musculoskeletal abnormalities. We also assess the role of the radiologist in the diagnosis, treatment, and preoperative evaluation of both primary and secondary IFI.
Ischiofemoral impingement Impingement Deep gluteal syndrome Quadratus femoris muscle External rotators Sciatic nerve Sciatic neuritis Piriformis syndrome Hip. Hip pain Injection test
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Conflict of interest
The authors declare that they have no conflicts of interest.
Human and animal rights and informed consent
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
All authors have no financial relationships to disclose.
Video 1Ultrasound (US) video shows a normal ultrasound study in this 65-year-old man found to have impingement changes on MRI. Note the impact of the ischial tuberosity (located on the left hand side of the image) and the lesser trochanter (located on the right) with the consequent entrapment of the QFM, which comes between them. Also note the posterior excursion of the sciatic nerve when the lesser trochanter approaches the ischial tuberosity. (MP4 6634 kb)
Video 24D-high-resolution multidetector CT video. Specific software generated this model of dynamization and preoperative templating of extra-articular impingement. (MP4 1857 kb)
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