This is a case of internal snapping hip (coxa saltans). The internal snapping hip syndrome has several proposed etiologies including the iliopsoas tendon over the iliopectineal eminence, iliopsoas muscle belly, or the femoral head. Physical examination of the snapping phenomenon is carried out with the patient supine by flexing the affected hip more than 90 degree and extending to neutral position. It can be accentuated by adding abduction and external rotation in flexion (FABER) and adducting and internally rotating while extending. The iliopsoas tendon is located lateral to the iliopectineal eminence when the hip is in full flexion, and may "snap" medially as the hip is extended back to neutral position. The snapping phenomenon can occur without pain in up to 10% of the general population and should be considered a normal occurrence. While the diagnosis is usually made clinically, ultrasound is a dynamic imaging modality which can observe tendons in motion. Alternatively, bursography (which is fluoroscopy with an injection of radio-opaque contrast into the bursa) can be used but does involve radiation to the pelvis. No mention is made of pain and the internal rotation impingement position does not cause pain, making hip labral tear less likely. External snapping involves a tight IT band laterally and is usually visible on examination.
Gruen et al describe the treatment of 30 patients with internal snapping. Sixty-three percent improved with nonoperative treatment, and the remainder did well with open surgical lengthening.
Ilizaliturri et al. randomized patients with internal snapping to endoscopic iliopsoas lengthening performed either via a lesser trochanter or trans-capsular approach. No difference was seen.
Illustration A shows the relationship of the iliopsoas tendon with the hip flexed, abducted and externally rotated on the left. The right side shows the position once the hip has been brought back to neutral, and during the transition between the two is when a "snap" may be elicited.
Illustration B shows a left hip in the neutral position, hyperechoic oval-shaped iliopsoas tendon (arrow) is located anterior to superior pubic ramus (SPR) and posterior to hypoechoic iliac muscle (m and arrowhead). Video A demonstrates the progression of motion from neutral to FABER and then back to neutral with a snapping of the iliopsoas tendon back to its original position at the end of the cycle.
Garrick JG (ed): Orthopaedic Knowledge Update: Sports Medicine 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 139-153.
Gruen GS, Scioscia TN, Lowenstein JE: The surgical treatment of internal snapping hip. Am J Sports Med 2002;30:607-613.
PMID:12130417 (Link to Abstract)
Ilizaliturri VM Jr, Chaidez C, Villegas P, Briseño A, Camacho-Galindo J. Prospective randomized study of 2 different techniques for endoscopic iliopsoas tendon release in the treatment of internal snapping hip syndrome. Arthroscopy. 2009 Feb;25(2):159-63. Epub 2008 Oct 10.
PMID:19171275 (Link to Abstract)