Comparison of MRI graded cartilage and MRI based volume measurement in knee osteoarthritis

The aim of this study was to investigate the relationship between the femoral, tibial and patellar cartilage volume and MRI grading of the articular cartilage in patients with knee OA.

Articular cartilage volumes of 65 postmenopausal women were determined by processing images acquired in the sagittal plane using a fast spin echo proton density-weighted sequence. The articular cartilages were divided into 5 compartments including lateral and medial tibial, lateral and medial femoral and patellar compartments. The articular cartilages were graded using a modified Outerbridge classification. Grade 0 indicated intact cartilage, grade 1 chondral softening with normal contour, grade 2 superficial fraying, grade 3 surface irregularity and thinning and grade 4 full thickness cartilage loss. The grades of articular cartilage were compared with cartilage volume measurements.

In medial femoral cartilage, grade 1 had more volume compared to grade 0 cartilage (p: 0.017). In medial tibial cartilage, grade 1 had more volume compared to grade 0 and grade 2 cartilage (p: 0.045 and p: 0.027, respectively). In patellar cartilage, grade 1 cartilage had significantly more volume than grade 0 cartilage (p: 0.007). In lateral tibial and femoral cartilages, no significant difference was observed between grade 0 and grade 1 cartilage.

Cartilage volume correlates well with MR grading of articular cartilage. The higher the grade of the cartilage the less the volume, with the exception of grade 1 lesions. Grade 1, reflects oedema in the cartilage and has a conflicting effect on volume measurement. The combination of MRI based volume measurement and grading of articular cartilage may provide an accurate method for the non-invasive evaluation and follow-up of articular cartilage.