Snapping Hip Syndrome

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This is a symptom complex characterized by pain and an audible or perceived snapping of the hip during movement such as exercise. It has various causes, which have been categorized as external, internal, and intra-articular.

Snapping Hip Syndrome CausesAnterior Inferior Iliac Spine Apophysis

Fig. 6. Avulsion of the anterior inferior iliac spine apophysis (AIIS) in an adolescent. (A) Longitudinal ultrasound showing anteriorly displaced apophysis. Arrow, avulsed, displaced apophysis; notched arrow, AIIS; open arrow, femoral head. (B) Longitudinal ultrasound of normal apophysis on asymptomatic side. Arrow, normal apophysis. (C) Fat-saturated, T2-weighted sagittal of avulsed apophysis. Image has been rotated for comparison to the ultrasound. (Courtesy of Theodore Miller MD, North Shore University Hospital, Great Neck, NY).

Fig. 6. Avulsion of the anterior inferior iliac spine apophysis (AIIS) in an adolescent. (A) Longitudinal ultrasound showing anteriorly displaced apophysis. Arrow, avulsed, displaced apophysis; notched arrow, AIIS; open arrow, femoral head. (B) Longitudinal ultrasound of normal apophysis on asymptomatic side. Arrow, normal apophysis. (C) Fat-saturated, T2-weighted sagittal of avulsed apophysis. Image has been rotated for comparison to the ultrasound. (Courtesy of Theodore Miller MD, North Shore University Hospital, Great Neck, NY).

The external type of snapping hip is the most common, and is caused by catching of either the posterior iliotibial band (ITB) or the anterior aspect of the gluteus maximus muscle as it moves over the greater trochanter during flexion and extension of the hip joint [16]. An external snapping hip is typically a clinical diagnosis, so imaging is seldom needed.

Intra-articular causes of a snapping hip include labral tears, loose bodies, synovial osteochondromatosis, and synovial folds. Hip MR arthrography is commonly used to assess for these intra-articular conditions [16-20].

An internal snapping hip is most commonly related to the iliopsoas tendon. Sonography has emerged as the preferred technique for examining the iliopsoas tendon, because it allows both static and dynamic evaluation of the soft tissues around the hip joint [16,20,21]. Sonography also provides an accurate method for injection into the iliopsoas bursa; however, because sonography may not allow accurate evaluation of intra-articular pathologic conditions, some combination of radiography, hip arthrography, CT, or MRI is still recommended if an intra-articular cause for hip pain is suspected [21].

The anterior aspect of the symptomatic hip is examined first using transverse and sagittal planes with the patient in the supine position. Static images are obtained along the course of the iliopsoas tendon down to the insertion onto the lesser trochanter (Fig. 7). Color Doppler is used to evaluate the tendon and peritendinous tissues for any increased vascularity to evaluate for tendinosis or bursitis.

Before the dynamic assessment of the iliopsoas tendon, patients should be asked if they are able to voluntarily reproduce their snapping sensation, and if so, what maneuvers elicit the snapping. The patient should then be asked to perform these maneuvers during dynamic imaging. If the patient cannot voluntarily reproduce snapping of the hip, he should be placed supine on the examination table and instructed to move the hip from a position of external rotation and slight flexion/abduction into a neutral position of extension and adduction [21]. When patients with a snapping hip perform this maneuver, snapping is manifested on sonography by a sudden rapid medial or rotatory movement of the tendon as it passes from lateral to medial [19,21,22].

Therapeutic injection (Fig. 8) into the iliopsoas bursa may delay or obviate surgery [22]. The relative ease of the procedure, coupled with a very low morbidity, makes it an excellent choice in the treatment of refractory iliopsoas ten-dinopathy or bursitis [23].

Sonography Gluteal Bursa

Fig. 7. Normal iliopsoas tendon. (A) Transverse sonographic image at the level of the acetabular rim best demonstrates the musculotendinous junction. The iliopsoas tendon (large arroW) has a normal echogenic appearance, iliopsoas muscle (small arrow), and acetabular rim (notched arroW) is seen as an echogenic line. (B) Longitudinal sonographic image of the iliopsoas tendon (arrows). Note the uniform echogenicity of the tendon.

Fig. 7. Normal iliopsoas tendon. (A) Transverse sonographic image at the level of the acetabular rim best demonstrates the musculotendinous junction. The iliopsoas tendon (large arroW) has a normal echogenic appearance, iliopsoas muscle (small arrow), and acetabular rim (notched arroW) is seen as an echogenic line. (B) Longitudinal sonographic image of the iliopsoas tendon (arrows). Note the uniform echogenicity of the tendon.

Iliopsoas Tendon Injection

Fig. 8. Iliopsoas bursa injection. (A) Transverse sonographic image during injection of the iliopsoas bursa demonstrates the needle (large arrows) within the bursa at the level of the acetabular rim (notched arroW) posterior and adjacent to the iliopsoas tendon (small arroW). (B) Transverse post-injection image shows fluid around the iliopsoas tendon. Small arrow, iliopsoas tendon; notched arrow, acetabular rim; arrowhead, fluid surrounding the iliopsoas tendon within the bursa.

Fig. 8. Iliopsoas bursa injection. (A) Transverse sonographic image during injection of the iliopsoas bursa demonstrates the needle (large arrows) within the bursa at the level of the acetabular rim (notched arroW) posterior and adjacent to the iliopsoas tendon (small arroW). (B) Transverse post-injection image shows fluid around the iliopsoas tendon. Small arrow, iliopsoas tendon; notched arrow, acetabular rim; arrowhead, fluid surrounding the iliopsoas tendon within the bursa.

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