In view of its usage requirement and load characteristics, the knee is the most common joint to be replaced due to development of arthrosis. Arthroplasty has presented functional and successful solutions for painful and motion-limited joints. However, together with the general health problems in these patients, many new problems Objective: The purpose of this study was to investigate the diagnostic efficacy of standard magnetic resonance imaging (MRI) and plain radiographs in determining the

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... tus of anterior cruciate ligament (ACL) for surgical decision-making processes in cases of medial unicompartmental knee arthroplasty (UKA). Methods: A total of 59 knees of 36 consecutive patients who underwent knee replacement surgery were analyzed retrospectively. MRI scans were assessed independently by 3 observers (radiologists), while the plain radiographs were evaluated by an independent radiologist. Results were compared with the intraoperative ACL status. Cross tabulation was used for descriptive statistics to analyze sensitivity, specificity, and accuracy of MRI and plain radiographs. Results: When the same observer assessed and classified the MRI twice, the reproducibility of the classification system varied from moderate to excellent. However, the interobserver concordance was moderate. The sensitivity of MRI was 73% and the specificity was 81%, while the sensitivity and specificity of plain radiographs was 36% and 79%, respectively. The accuracy of MRI was 80%, while that of the radiographs was 71%. Conclusion: Detection of intact ACL may be possible on available plain radiographs without necessity for additional means such as MRI, which may cause increase costs and loss of time. In cases where there is uncertainty regarding ACL integrity in degenerative knees, although standard MRI provides additional information on ACL status, it is not of sufficient diagnostic value.