PMC4282225_01
Ultrasonograms of a 20-year-old man with snapping elbow.. A. On the longitudinal scan of anterolateral elbow, the proximal edge of thickened annular ligament (arrows) is slipped into the radiocapitellar joint in extended elbow. Note the distal portion of the ligament is still attached at radial neck. B. During elbow flexion, the thickened annular ligament (arrowheads) relocates in front of the radial head. C, capitellum; R, radial head.
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And the annular ligament slipped out of the radiocapitellar joint, relocated in front of the radial head during elbow flexion (Fig. 1, Electronic Supplementary Video 1).
Arthroscopic images of snapping annular ligament in the radiocapitellar joint.. A. Thickened annular ligament (arrows) partially covering radial head articulating surface is visible from a proximal anteromedial portal in extended elbow. B. During elbow flexion, the proximal edge of thickened annular ligament (arrows) is repositioned out of the radiocapitellar joint, visualizing the smooth margin of radial head articulating surface. C. Resection of the proximal edge of thickened annular ligament revealed no more slipping into radiocapitellar joint in elbow extension.
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Arthroscopy revealed hypertrophied leading edge of annular ligament, which is proximally migrated between radial head and capitellum in elbow extension (Fig. 2A) and repositioned anterior to radial head in elbow flexion (Fig. 2B).