Chronic irreducible posterolateral knee dislocation: two-stage surgical approach.

Posterolateral knee dislocation is a small subset of knee dislocations. Irreducible posterolateral dislocation has been reported and is caused by buttonholing of the medial femoral condyle into the anteromedial knee capsule, with interposition of the medial retinacular structures between the femoral and tibial condyles. Open reduction has been advocated to reduce the knee. We present a case of chronic irreducible posterolateral dislocation of the knee for 14 months associated with anterior and posterior cruciate ligament (ACL, PCL) and medial collateral ligament (MCL) rupture. The patient presented with continued instability. The classic dimple sign was absent in this case because of chronicity, but the limb was in valgus alignment compared with the other side. The magnetic resonance imaging (MRI) report commented only on the torn cruciates and the MCL, but missed the tissues preventing reduction. A 2-stage surgical procedure was performed. The first stage included arthroscopic debridement of the intervening tissues, which were thickened and resembled meniscal tissue, followed by reduction of the knee and open MCL repair to maintain the reduction. The second stage was done for ACL and PCL reconstruction. In conclusion we bring the attention of the surgeon to the clinical, radiographic, and MRI findings associated with this chronic irreducible posterolateral knee dislocation.