To explore the short- and mid-term effectivenesses of combined unicompartmental knee arthroplasty (UKA) and anterior cruciate ligament (ACL) reconstruction for osteoarthritis (OA) and ACL injury.Between January 2006 and January 2014, 32 patients with knee OA and ACL injury were treated by combined UKA and ACL reconstruction. There were 12 males and 20 females, aged 41-63 years (mean, 50 years); 17 left knees and 15 right knees were involved. The causes of ACL injury were sports injury (25 cases) and traffic accident injury (7 cases), including 27 cases of old injury and 5 cases of acute injury. Pain of the medial compartment of the knee and unstable knee joint were the main clinical symptoms. Preoperative X-ray films showed (3.1 ± 0.6)° of varus deformity.All incisions healed by first intention, without complication. The patients were followed up 16-112 months (mean, 55 months). Mobile bearing dislocation occurred in 2 cases after operation, and was cured after replacing much thicker mobile bearings. X-ray films showed (4.0 ± 0.7)° of valgus at last follow-up. There was no loosening of the prosthesis. Physiological radiolucent line (< 1 mm) was observed around the tibial component in 10 patients. The Oxford Knee Score (OKS), Knee Society Score (KSS) clinical score, KSS functional score, and Tegner activity score at last follow-up were improved significantly (P < 0.05). The range of motion (ROM) of the operated knee was (123.5 ± 2.8)°, and the posterior slope of the tibial component was (3.9 ± 1.2)° at last follow-up; a significant correlation was found between ROM and posterior slope according to the Pearson's correlation (r = 0.392, P = 0.031).Combined UKA and ACL reconstruction has good short- and mid-term effectivenesses for OA and ACL injury.