It is unclear why there are compartmental differences in the risk of knee osteoarthritis (OA). We investigated whether there are compartment differences in the volume of knee cartilage in healthy persons and identified determinants of medial and lateral tibial cartilage volume.
A total of 166 healthy persons (age range 21-79 yrs, 58% female) with clinically and structurally normal knees were examined. Thickness and volume were determined for the medial and lateral tibial articular cartilages by processing images acquired in the sagittal plane using T1 weighted fat saturated magnetic resonance imaging on an independent work station.
In every subject, the lateral tibial cartilage was thicker than medial cartilage (mean 6.43 +/- SD 1.25 mm vs 4.49 +/- 0.81 mm; p < 0.001), and the volume of cartilage was greater (2.34 +/- 0.70 ml vs 1.82 +/- 0.56 ml; p < 0.001). This effect persisted when values for men and women were analyzed separately. Both medial and lateral tibial cartilage volume and thickness were greater in men compared to women, independent of body mass index and bone size. The reduction in medial and lateral tibial cartilage volume and thickness was inversely related to the current level of physical activity.
This study supports the knee compartment differences in cartilage volume recently reported in children. It is likely these differences are maintained throughout life. The possibility that the amount of knee cartilage in an individual is a risk factor for OA now needs to be tested in longitudinal studies.