Horizontal intra-articular patellar dislocation resulting in quadriceps avulsion and medial patellofemoral ligament tear: a case report.

Intra-articular patellar dislocations are rare. We present a 13-year-old boy who sustained a complete horizontal intra-articular patellar dislocation following blunt trauma to the flexed knee. Closed reduction was unsuccessful and open reduction indicated a repairable quadriceps avulsion and medial patellofemoral ligament tear. He is the youngest patient to sustain a quadriceps rupture and the only patient to sustain a medial patellofemoral ligament tear to date. His flexed knee and the horizontally positioned patella (seen on lateral radiograph) were indicative of a complete rotational injury with extensor mechanism involvement. Open reduction allowed for the repair of both injuries and a favorable outcome.