Knee dislocation with concomitant multiligament injury is a rare and devastating injury. We report the successful repair of a rare case of open knee dislocation with concomitant multiligament injury and patellar tendon rupture of an 18-year-old male due to a motorcycle accident. The patient presented with an open wound running parallel to the knee joint line and patellar tendon rupture with full exposure of the cartilage of the distal femur. Staged surgical management including the application of a ring-type external fixator with a hinged joint, lateral collateral ligament repair, medial collateral ligament reconstruction using autogenous hamstring tendon, and joint release was performed. Range of movement was recovered to 0 degrees of knee extension and 80 degrees of knee flexion, and extension lag was negative. The Lysholm score of the patient was recovered to 92. The patient was able to return to work in the construction field 2 years after sustaining the injury. The patient had no complaint of pain and was able to resume construction work, even though reconstruction of the anterior cruciate ligament and posterior cruciate ligament was not performed. The application of a hinged ring-type external fixation device might play a key role in early range of movement restoration and to maintain the reduced position and acceptable recovery of the posterior cruciate ligament injury without the need for reconstructive surgery. This report is the first to describe the safety and effectiveness of staged surgical management for the repair of open knee dislocation with concomitant multiligament injury and patellar tendon rupture. However, further studies with longer follow-up periods will be needed to observe the development of osteoarthritis or weakness of the knee. Staged surgical management is a safe and effective procedure for repairing an open knee dislocation with concomitant multiligament injury and patellar tendon rupture.