Although the bony structure of the knee joint is unstable, there are strong ligaments and muscles protecting the joint and the anterior segment, so knee dislocation is relatively rare. Occasionally, dislocation occurs when a strong direct violent impact on the upper end of the tibia or indirect violence causes the knee joint to be rotated or hyperextended, causing the upper end of the tibia to dislocate backward and forward (Figure 1). In the case of complete dislocation, not only the joint capsule is ruptured, but also the cruciate ligament, medial and lateral collateral ligament, meniscus and surrounding muscles are torn; even combined with avulsion fractures of the tibial spine, tibial tuberosity and femoral condyle fractures. Severe medial dislocation may cause traction injury to the common peroneal nerve. Severe posterior dislocation may cause rupture, embolism, and compression of the popliteal artery and vein, causing limb necrosis and ischemic contracture.