Objective To observe the effectiveness of the combination of dynamic and static stabil ity in the treatment of old knee medial collateral l igament injury. Methods Between March 2004 and June 2008, 26 cases of old knee medial collateral l igament injury were treated, including 19 males and 7 females with a mean age of 38 years (range, 21-48 years). Injury was caused by traffic accident in 6 cases, by sprains in 12 cases, by fall ing from height in 8 cases. The location was left knee in 15 cases and right knee in 11 cases. Of them, 24 patients showed the positive result of knee valgus test, 2 cases showed sl ightly relaxed knee tendon. The knee X-ray films of valgus stress position showed that the medial joint space differences between both knees were 3-5 mm in 2 cases and 5-12 mm in 24 cases. The injuries included avulsion of the medial femoral condyle starting point in 19 cases, central laceration in 6 cases, and tibial point laceration concomitant meniscus injury in 1 case. The time from injury to hospital ization was 3-14 months (mean, 6.4 months). Gracil is muscle was used to repair knee medial collateral l igament and the sartorius muscle transfer to reconstruct the medial rotation of knee stabil ity function. Results All incisions healed by first intention. No joint infection, deep vein thrombosis, or other postoperative compl ications occurred. Twentysix cases were followed up 12-58 months with an average of 30 months. The results of knee valgus stress test were negative with no joint tenderness. At 3 months after operation, the knee X-ray films of valgus stress position showed the medial joint space differences between both knees were less than 1 mm. According to the modified Lysholm-Scale score, the results were excellent in 18 cases, good in 7 cases, and fair in 1 case with an excellent and good rate of 96% at last follow-up. Conclusion A combination of dynamic and static stabil ity in repairing old knee medial collateral l igament injury is easy-to-operate and has the advantages to perform the operation in the same incision, so it can avoid the shortcomings of single repair method and achieve better effectiveness.