The meniscal pathology of the knee is one of the clinical realities the orthopedic surgeon must daily confront with. The diagnosis is generally both clinical and instrumental; among the different diagnostic imaging techniques, Magnetic Resonance Imaging (MRI) appears to be the most accurate method regarding sensitivity and specificity for the study of meniscal fibrocartilages and articular cartilage. In an attempt to clarify the roles of MRI and diagnostic knee arthroscopy, we performed a retrospective comparative study of the two methods to assess their sensitivity and specificity in the diagnosis of meniscal pathology. We evaluated 105 consecutive patients with a clinical diagnosis of intra-articular knee pathology who were subjected to MRI examination and subsequently to surgical arthroscopy, recording on a graphic card the surgical and radiographic findings expressed by a blinded expert radiologist. Comparison of MRI and arthroscopy data showed, for the internal meniscus, values of 98.5% sensitivity, 94.7% specificity and 93.8% "K" index for MRI compared to arthroscopy, and of 90%, 98.6% and 90.5% for the external meniscus. These results allow us to state that the diagnostic capacity of MRI appears to be very high and therefore crucial in the planning of the correct surgical treatment of individual patients, thanks to its ability to highlight even small changes affecting intra-articular structures.