ObjectiveTo evaluate the clinical results of the tibial Inlay technique for the medial collateral ligament (MCL) reconstruction using Achilles tendon allograft in recovery of medial instability of the knee. MethodsBetween January 2011 and December 2012, 21 patients underwent tibial Inlay reconstruction of the MCL using Achilles tendon allograft, and the clinical data were retrospectively analyzed. There were 13 males and 8 females with a mean age of 32 years (range, 19-62 years). Injury was caused by sports in 15 cases and by traffic accident in 6 cases. The disease duration ranged from 15 days to 3 months (mean, 1.5 months). According to International Knee Documentation Committee (IKDC) criteria, 5 cases were classified as degree II and 16 cases as degree III. The results of the valgus stress test were positive in all patients. The complications were observed after operation; IKDC subjective knee score and Lysholm score were used to assess the knee function. ResultsBone block fracture occurred in 1 case during operation. Primary healing of incision was obtained in the other cases except 1 case having unhealing incision who was healed after skin grafting. No complications of knee joint stiffness, vascular nerve injury, and infection occurred. All patients were followed up 7-29 months (mean, 18.5 months). At last follow-up, the results of the valgus stress test were negative in 20 cases, and positive (degree I) in 1 case; the other patients had no knee extension or flexion limitation except 1 patient having 15° flexion limitation. The Lysholm score was significantly improved from 45.4±13.6 to 87.5±9.4, the IKDC 2000 subjective score was significantly improved from 46.5±14.0 to 88.4±9.3 at last follow-up (P<0.05). MRI showed that the reconstructed MCL was continuous. ConclusionThe short-term clinical results of the tibial Inlay technique for MCL reconstruction using Achilles tendon allograft are satisfactory. The Inlay technique for MCL reconstruction can provide good medial stability of the knee, but the lorg-term effectiveness needs further follow-up.