Pellegrini-Stieda ossification can also involve the posterior attachment of the MPFL

To evaluate for development of Pellegrini-Stieda (PS)-type ossification following injury to the posterior attachment of the medial patellofemoral ligament (MPFL).

This retrospective study evaluated 27 patients with acute knee injury with initial radiographs, magnetic resonance imaging within 1 week of injury, and follow-up radiographs assessing for development of PS.

Of the 27 patients who developed PS ossification, 7 patients (25.9%) had isolated MPFL injury with the ossification slightly more proximal than the traditional PS.

Isolated injury to the posterior MPFL also leads to PS ossification, which is slightly superior in location to the traditional PS.