Complete dislocation of the knee without disruption of both cruciate ligaments

Complete dislocation of the knee is recognized to be an extremely severe injury, representing one of the few true orthopedic emergencies. There is major trauma to the ligaments, capsule, and tendons, with a high incidence of associated damage to the popliteal artery and peroneal nerve. Resulting disability can be great, reflected by pain, stiffness, or instability of the knee; neurologic deficits in the foot and ankle; and even amputation if the vascular injury is not addressed promptly. Most accounts of knee dislocations in the literature have suggested that disruption of both cruciate ligaments is necessary for a complete dislocation to occur. This consensus is based on clinical observations and some laboratory investigations of ligament failure patterns. This report presents four cases of complete tibiofemoral knee dislocation without disruption of both cruciate ligaments. We also review the literature on knee dislocations with an emphasis on the biomechanics of soft tissue restraints about the knee and analyze how sufficient laxity can occur, with one cruciate ligament remaining intact, to allow for complete knee dislocation.