MR imaging of calcification of the lateral collateral ligament of the knee: a rare abnormality and a cause of lateral knee pain.

OBJECTIVE: Our objective was to describe the radiologic appearances of calcification of the lateral collateral ligament (LCL) of the knee in four patients who presented with acute atraumatic lateral knee pain. This rare abnormality has not, to our knowledge, been previously shown on MR imaging.
CONCLUSION: Calcification of the LCL of the knee is a rare cause of lateral knee pain and is thought to reflect underlying hydroxyapatite deposition. On MR imaging, calcification of the LCL may be associated with an aggressive appearance that can be mistaken for other knee abnormalities.