MR in the study of knee cartilage pathologies: influence of location and grade on the effectiveness of the method.

Purpose: To evaluate the diagnostic effectiveness of magnetic resonance (MR) in knee cartilage pathologies of different regions and grades with the aim of establishing the role of MR in treatment choice.

Materials And Methods: We enrolled 90 patients who underwent MR and arthroscopy of the knee. To classify cartilage lesions we used a simplified grading system that correlates MR to arthroscopic reports and divides lesions into low and high grades. The MR examinations were performed with a 1.5 T superconducting magnet with a standard protocol to obtain quality images in a short time, using T1-weighted spin-echo sequences, T2* weighted gradient-echo sequences and inversion recovery sequences. The MR diagnostic specificity, sensitivity and accuracy and MR positive predictive value and negative predictive value in identifying and grading the chondral lesions of the femorotibial and patellofemoral compartments were calculated and compared to arthroscopy parameters.

Results: The analysis of each grade of chondral lesions reveals an MR accuracy of 94% in high-grade lesions of the femorotibial and patellofemoral compartments and an MR accuracy of 78% in low-grade lesions of patellofemoral compartment and of 70% in low-grade lesions of femorotibial compartment. This result suggests MR is useful for the grading of chondral lesions in clinical practice.

Conclusions: MR diagnostic effectiveness substantially changes according to the different location and grade of chondral lesions. While MR seems to be nearly equivalent to arthroscopy for high-grade lesions subject to surgery, it appears to be less accurate in diagnosing low-grade lesions, in particular femorotibial lesions.