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Extraarticular snapping hip: sonographic findings.

OBJECTIVE
The aim of the study was to determine the sonographic findings of snapping hip and to correlate the findings with the presence or absence of pain.


MATERIALS AND METHODS
Twenty patients with snapping hip were examined with sonography. Conventional and dynamic sonographic examinations of both hips were performed using a 5.0- or 7.0-MHz transducer.


RESULTS
Conventional sonographic studies allowed identification of various structural abnormalities (tendinitis, bursitis, synovitis) and helped to document tenderness along the course of specific tendons. Dynamic sonographic studies revealed 26 cases of snapping hip. In 24 of these 26 cases, the underlying cause was clearly identified. Twenty-two snapping hips were caused by an abnormal movement of the iliopsoas tendon, and two were caused by iliotibial band friction over the greater trochanter. One patient reported a bilateral snapping sensation that could not be documented on sonography. Snapping hip was elicited by a wide variety of hip movements. Sonography established an immediate temporal correlation between the jerky tendon motion and the painful snap reported by the patient. Only 14 cases of snapping hip were painful.


CONCLUSION
Conventional sonographic studies can identify signs of tendinitis, bursitis, or synovitis. Dynamic sonographic studies revealed the cause of snapping hip in most patients. Snapping hip is characterized on sonography by a sudden abnormal displacement of the snapping structure. In our study, a significant proportion of the cases of snapping hip were not painful.