Objective To investigate the effectiveness of reconstructing medial patellofemoral l igament with hamstring tendon autografts for the treatment of recurrent patellar dislocation under arthroscopy. Methods Between January 2005 and January 2010, 22 cases of recurrent patellar dislocation were treated by lateral retinacular release and reconstructionof the medial patellofemoral ligament with hamstring tendon autografts under arthroscopy. There were 5 males and 17 females, aged 15-19 years (mean, 17.3 years). The average number of dislocation was 4 (range, 3-8). The main cl inical symptoms were pain and swell ing of knee joint, weakness in the leg, and limited range of motion (ROM). The patellar tilt test, pressing pain of patellofemoral ligament insertion, and apprehension sign showed positive results. According to International Knee Documentation Committee (IKDC) scoring criteria, the subjective IKDC score was 36.7 ± 4.7, and the Lysholm score was 69.3 ± 3.8. X-ray films showed that the patella inclined outwards. Results All incisions healed by first intention. Twenty-two cases were followed up 18-49 months (mean, 34 months). Pain and swelling of knee joint and weakness were improved obviously. No recurrence was found during follow-up. The ROM of knee in flexion and extension was improved when compared with preoperative ROM. The subjective IKDC score was 92.4 ± 5.3 and the Lysholm knee score was 91.7 ± 5.2, showing significant differences when compared with preoperative scores (P lt; 0.05). Conclusion Reconstruction of the medial patellofemoral ligament with hamstring tendon autografts under arthroscopy is an effective method to treat recurrent patellar dislocation.