PURPOSE: The aim of this study is to determine the relationship between the arthritic changes and a deficiency of the anterior cruciate ligament (ACL) in osteoarthritic knees. MATERIALS AND METHODS: Between May 2003 and January 2008, 815 cases of total knee arthroplasty that were due to degenerative osteoarthritis of the knee were enrolled in this study. Flexion contracture, the tibia-femoral angle, translocation of the tibial spine and erosion on the posteromedial tibial plateau were assessed and we tried to determine the relationship between these findings and an ACL-deficiency. RESULTS: The mean flexion contracture in the knees with a deficient ACL was 10.7degrees and this was 8.8degrees in the knees with an intact ACL, and this difference was statistically significant (p=0.001). The tibia-femoral angle of the patients with an ACL-deficiency was 7.97degrees varus on average, and that for patients with an intact ACL was 4.38degrees varus, and the difference was found to be highly dependent upon the ACL's integrity (p=0.000). 77.6% of the knees with varus deformity exceeding 15degrees showed an abnormal ACL. Translocation of the tibial spine doesn't predict ACL integrity. Bone erosion on the posteromedial tibial plateau was significantly frequent in patients with ACL-deficient knees (p=0.000). For the knees with erosion on the posteromedial tibial plateau, 85% of these knees showed an ACL deficiency. CONCLUSION: Varus deformity exceeding 15degrees and erosion on the posteromedial tibial plateau can reflect ACL deficiency.