Tibial collateral ligament bursa: MR imaging.

The bursa of the tibial collateral ligament (TCL) may be visualized at magnetic resonance (MR) imaging when it becomes distended with fluid. In the authors' experience, this finding signifies a pathologic condition either in the medial capsuloligamentous complex or in the bursa itself. Such a finding may indicate TCL bursitis. TCL bursitis can be suspected in the setting of isolated pain in the medial joint line in the absence of mechanical symptoms. Prolonged relief of symptoms after injection of steroid into the bursa is supportive of the diagnosis. Seven cases are presented in which a fluid-filled TCL bursa was identified at MR imaging. In five cases, TCL bursitis was suspected. The differential diagnosis for the MR findings is discussed.