Acute thumb injury. Swelling & tenderness over medial aspect of MCPJ1.
Comparison long-axis ultrasound images of the UCL at MCPJ1 are shown. On the abnormal right side, an ovoid mass-like thickening which includes and overlies the metacarpal origin of UCL (solid arrow) actually represents the displaced (proximally folded) distal stump of UCL [Stener lesion]. There is a surrounding collar of haemorrhagic thickening and a markedly hypoechoic zone of absent ligamentous fibres in the expected location of the distal UCL segment (dashed arrow). Normal size, contour and echotexture of the proximal UCL is demonstrated by comparison on the left (arrowhead).
NOTE: UCL = ulnar collateral ligament