Method : The “internal fixation” is a purely arthroscopic procedure. Some rules have to be strictly respected : isometry, posterior tibial insertion, a straight alignment of the tibial and femoral tunnels when the knee is in flexion of about 50°, no tension at all of the artificial ligament while the repaired A. C. L. must be slightly tightened, no impingement with special attention to the roof of the notch. The intra articular “free fibers” structure of the artificial ligament(LARS-Ligament Advanced Reinforcement System) allows , with a smaller volume of synthetic material , a better permeability to fibroblastic ingrowth and a better resistance to fatigue specially to torsion.