The aim of this study is to assess the accuracy of clinical examination of the knee compared to MRI and Arthroscopy in diagnosing significant internal derangement.

We performed a retrospective analysis on 245 patients who underwent an MRI of the knee over a two-year period. The MRI diagnoses were compared with both clinical and arthroscopic findings. There were 169 male and 76 female patients with an average age of 33 years. A history of significant trauma was seen in 98 (40%) patients. The commonest clinical diagnosis was isolated medial meniscal tear (25%). Anterior cruciate ligament (ACL) tear was diagnosed in 8% and lateral meniscal tear in 7% of cases. No definite clinical diagnosis could be reached in 32% of patients. MRI showed no significant abnormality in 103 (42%) patients. Medial meniscal tear was noted in 47 (19%), ACL tear in 20 (8%) and lateral meniscal tear in 10 (4%) of the MRI scans. 96 patients (39%) proceeded to arthroscopy after their MRI scans. The mean time from MRI scan to arthroscopy was 181 days. The MRI and arthroscopy findings were in complete agreement in 90 (94%) patients. Of the 6 patients whose MRI findings did not correlate with arthroscopy, 4 showed meniscal tears not seen at surgery and two diagnosed ACL ruptures subsequently shown to be normal at arthroscopy. Three of the 4 meniscal tears were of the inferior surface of the posterior horn of the medial meniscus and one of the inferior surface of the lateral meniscus. The films were reviewed independently by three experienced MR radiologists all of whom confidently diagnosed a tear in each case.

Clinical examination alone is not satisfactory in the diagnosis of knee injuries. MRI is a highly sensitive tool for diagnosis. Injuries that are commonly missed at arthroscopy can be diagnosed easily with MRI.