We present the case of a preventive tibial plateau flexion osteotomy in an adolescent patient who had a reduced posterior slope of the tibial plateau. The patient was asymptomatic and without instability at the time. However, magnetic resonance imaging (MRI) showed a dysmorphic posterior cruciate ligament, which was interpreted as an indication for osteotomy. This article demonstrates the surgical technique and postoperative outcome. The postoperative MRI shows a reorganization of the posterior cruciate ligament into a physiological ligament appearance.