Objective To explore the cl inical effectiveness of arthroscopic reconstruction of medial patellofemoral l igament (MPFL) with trabs of medial soft tissues in the treatment of patellar instabil ity of adolescence. Methods From January 2005 to December 2006, 23 cases of patellar instabil ity were treated, including 10 males and 13 females with an average age of 16 years old (13 to 20 years old). The locations were left knee in 11 cases, right knee in 12 cases. The disease course was 1-28 weeks (mean 15 weeks). All patients had patellar instabil ity sense and knee arthralgia during strenuous exercise. Preoperative, the International Knee Documentation Committee (IKDC) score and Lysholm score were 48.30 ± 5.77 and 50.80 ± 7.61. The congruence angle, lateral patellar angle, and Q angle were (9.00 ± 2.46), (2.94 ± 2.55) and (19.10 ± 4.16)°. All of the patients experienced the operation of reconstruction of MPFL with trabs of medial soft tissues (medial patellar retinaculum, joint capsule and vastus medial is obl ique muscle fiber) through arthroscope. Results All the wounds healed by first intention, and no postoperative early compl ication occurred. All cases were followed up 19 months on average (12 to 24 months). Apprehensive test and patella tilt test were negative. The range of motion returned to normal. There was no recurrence of dislocation after operation. At 12 months after operation, the congruence angle, lateral patellar angle, and Q angle were (—7.03 ± 0.60), (11.00 ± 3.47) and (11.30 ± 1.90)°; the IKDC score and Lysholm score were 93.20 ± 3.51 and 94.10 ± 4.26. There were statistically significant differences between preoperation and postoperation (P lt; 0.05). Conclusion Arthroscopic reconstruction of MPFL with trabs of medial soft tissues can improved obviously the affected limb function in treatment of patellar instabil ity of adolescence.