Grade III distal medial collateral ligament rupture co-existing with transient lateral patellar dislocation.

Lateral patellar dislocations are the second most common type of traumatic knee injury, accounting for approximately 2-3% of cases, the most common being anterior cruciate ligament (ACL) injury. There are several well-documented anatomical risk factors predisposing to patellofemoral instability for example: patella alta, trochlear dysplasia, ligamentous laxity, and genu valgum. Co-existing medial collateral ligament injury in cases of patellar dislocations in the absence of ACL injury is uncommon and infrequently reported in the literature. The authors present a case of a 14-year-old boy presenting with a left knee injury while playing football who was diagnosed on magnetic resonance imaging (MRI) with a transient lateral patellar dislocation, high-grade medial patellofemoral ligament (MPFL) injury and a full thickness (grade III) injury to the distal medial collateral ligament.