Giant-cell tumor of the tendon sheath arising from the posterior cruciate ligament of the knee: a case report and review of the literature.

The localized form of a giant-cell tumor of the tendon sheath is uncommon and rarely intraarticular. While the sonographic findings are nonspecific, the magnetic resonance (MR) findings can be diagnostic. Relatively homogeneous iso- or marginal hyperintensity on T2-weighted sequences, lack of susceptibility effects due to hemosiderin, the demonstration of a fibrous capsule and the absence of adjacent joint involvement may help to differentiate localized and diffuse forms of giant-cell tumors of tendon sheaths and pigmented villonodular synovitis.