Tehran University Medical Journal

Background: The knee is the most commonly injured joint. The internal components of the knee include the meniscuses, the anterior cruciate ligament (ACL) and posterior cruciate ligaments (PCL). Magnetic resonance imaging (MRI) is now used widely because of its high accuracy and noninvasiveness. Our objective was to diagnose internal knee component injuries by MRI and compare its diagnostic value with that of arthroscopic surgery.
Methods: This process research study was carried out between May 2004 and September 2006 on 90 randomly selected patients admitted to the orthopedic ward of Baghiatollah Hospital, Tehran, Iran. Each patient had arthroscopic surgery after undergoing MRI by an expert radiologist.
Results: Out of 90 patients, 81 were male and nine were female. The mean age was 31.6 years (range: 17-71). Among patients with normal ACL as shown by MRI, 42.4% were shown by arthroscopy to have a ruptured ACL. The sensitivity and specificity of MRI in ACL abnormalities were 73% and 77%, respectively. Only 1.3% of the patients with normal PCL by MRI showed PCL rupture upon arthroscopic examination. The evaluation of the lateral meniscus by MRI had a sensitivity and specificity of 40% and 94%, respectively. Likewise, in the medial meniscus, sensitivity and specificity by MRI was 70% and 98%, respectively.
Conclusion: According to our study, considerable differences exist between MRI reports and arthroscopic findings in the diagnosis of internal knee injuries. We therefore conclude that sole reliance on MRI reports is not reasonable for making treatment decisions and MRI should be used as just one of the diagnostic tools, in conjunction with other methods, such as physical examination and arthroscopy.