OBJECTIVE: To present the surgical technique and follow-up results of anatomical reconstruction of the N-fibular ligament in the treatment of posterior external rotational instability of the knee. Methods From July 2003 to September 2006, a total of N-fibular ligament reconstructive surgery was used to treat posterior external rotation instability of the knee. A double bone tunnel was made through a lateral knee incision at the stop of the N-fibular ligament at the head of the fibula, and a bone tunnel was made at the beginning of the N-tendon on the femoral side, and the graft was selected from an autologous semitendinosus tendon or an allograft anterior tibial tendon. The ends of the graft were passed through the fibular head tunnel and then fixed in the femoral tunnel using an absorbable extrusion screw. Combined with other compound ligament injuries, simultaneous repair or reconstruction was performed. Results From July 2003 to September 2006, 19 cases of this procedure were completed, with a minimum follow-up of 1 year in 94.7% of cases (18/19) and a mean follow-up period of 27.2 months. All cases were old injuries and all were compound ligament injuries, including posterior cruciate ligament, anterior cruciate ligament, and medial collateral ligament. Preoperative tibial external rotation was greater than 10ºin all cases compared to the healthy side. All patients underwent preoperative and postoperative clinical examination, radiographs, and MRI. The final follow-up included IKDC subjective and objective scores, and a 30º tibial external rotation test examination with flexion of the knee. The results of the postoperative external tibial rotation test were: reduction of tibial external rotation angle by 0º~5º compared with the healthy side in 14 cases, reduction by 5º~10º compared with the healthy side in 3 cases, and reduction by 10º~15º compared with the healthy side in 2 cases. Preoperatively, all cases had an increase in tibial external rotation of 10ºor more. The mean limitation of knee flexion was 4.2° (0° to 10°). There were no cases of knee extension limitation. The postoperative IKDC score was grade A in 7 cases and grade B in 12 cases. Preoperatively, all cases were D. ConclusionThe N fibular ligament anatomical reconstruction technique is a good method for treating posterior external rotation instability of the knee joint of type A. The procedure is safe and simple, and a more satisfactory clinical outcome can be obtained.