Purpose: To determine the accuracy of knee examination under anesthesia (EUA) and develop a prognostic score for partial anterior cruciate ligament (ACL) tears. Materials and Methods: A total of 229 patients with an ACL injury were included. Knee EUA was performed using the Lachman test, pivot shift test and arthrometric maximum manual side-to-side difference (AMMD) test. The arthroscopic examination is the gold standard for the diagnosis of partial and complete ACL tears, which was compared with EUA findings. Multivariate logistic regression was estimated, and the significant variables were used to develop a predictive score. Results: The relative risk for a complete tear with Lachman 2+ was 8.55 (range, 3.5 to 20.7) and 53.04 (range, 6.7 to 417) with Lachman 3+, compared to Lachman 1+. Negative pivot shift was reported in 23 cases in the partial tear group (76.7%) and in 22 in the complete tear group (11.1%). The AMMD was 3.5 mm in the partial tear group and 5.4 mm in the complete tear group (p<0.05). A prognostic score of less than five suggested the presence of a partial ACL tear. The score showed 81.1% sensitivity and 68.7% specificity. Conclusions: Partial ACL tears can be differentiated from complete tears with Lachman test, pivot shift test, and AMMD test.