Posteromedial Knee Capsule Tear Without Concomitant Ligament Rupture or Meniscal Pathology in a Pediatric Athlete

The posterior knee capsule is a critical structure for tibiofemoral stability, limiting hyperextension, and posterior translation. Injuries to this structure are rare and typically occur alongside anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) tears. To date, no cases have been reported of a posteromedial capsule tear without concomitant ligamentous rupture or meniscal injury, leaving its clinical significance and optimal management unclear. We report on a 15-year-old male who sustained a hyperextension knee injury while playing basketball, presenting with pain and an abnormal gait. Diagnostic arthroscopy revealed an intact ACL and a full-thickness 3 cm posterior capsule tear, which was repaired arthroscopically. At 6 months postoperative, mild recurvatum persisted. This case parallels ramp lesions, another posteromedial injury with, at times, conflicting management guidelines. This case underscores the need for further research into the diagnosis, management, and long-term outcomes of posterior capsule injuries given that they are poorly understood in isolation due to their frequent association with multi-ligamentous trauma. Future studies should aim to evaluate best practice and determine whether surgical intervention is necessary or if conservative management could yield comparable results.