History features: ①A history of trauma is also necessary, either as a sprain, more often as a kneeling injury or traffic injury. ② Post-injury is accompanied by joint swelling and pain, which improves after rest. ③ posterior cruciate ligament injury after a certain degree of self-healing ability, chronic symptoms depending on the amount of function of the residual posterior cruciate tract, can be almost asymptomatic, or painful, or even obvious signs of instability. Physical examination is relatively simple and relatively specific: the posterior drawer test is positive, and some patients will have a false negative if they have a partial rupture or a certain amount of scar healing after the rupture. MRI often shows loss or disruption of the posterior cruciate ligament-specific low signal contour and, in a few cases, swelling. Arthroscopic reconstructive surgery after cruciate ligament injury has become routine, and the first choice of reconstructive material remains autologous tissue, including the middle 1/3 of the patellar tendon, the N cord, the Achilles tendon, and the quadriceps tendon, with the N cord being the most commonly used. In cases of multi-ligament injuries, homogeneous allogeneic tissues and artificial tendons can be used as a complement. Reconstruction methods have been differentiated between single-tunnel and double-tunnel reconstruction. Double-tunnel reconstruction has advantages in theoretical and biomechanical tests, but there is no significant difference in postoperative knee stability and subjective patient satisfaction in clinical follow-up, and its advantages have not yet been recognized.