Sex and site differences in cartilage development - A possible explanationfor variations in knee osteoarthritis in later life

Objective, To test the hypothesis that sex-related and joint compartment-re lated differences in the risk of osteoarthritis (OA) of the knee might be a ssociated with variations in cartilage development, we investigated knee ca rtilage volume in healthy children. Methods, We studied 92 children who were randomly selected from among stude nts in grades 3-12 of a single school in Hobart, Tasmania (49 boys, 43 girl s; age range 9-18 years). Articular cartilage thickness and volume were det ermined at the patella, medial tibial compartment, and lateral tibial compa rtment by magnetic resonance imaging (MRI), Sagittal T1-weighted fat-suppre ssed MRI images were obtained and processed on an independent computer work station. Results, Males had significantly more knee cartilage than females. Sex acco unted for 6-36% of the variation in cartilage thickness and volume, which w as statistically significant at all sites. Even after adjustment for age, b ody mass index, bone area, and physical activity, males had 16-31% higher c artilage volume; this was most marked at the medial tibial site. In additio n, lateral tibial thickness was greater than medial tibial thickness (5.9 v ersus 3.6 mm; P < 0.0001) and lateral tibial volume was greater than medial tibial volume (2,823 versus 2,299 <mu>L; P < 0.0001), Furthermore, physica l activity was a significant explanatory factor for cartilage volume at all sites (R-2 7-14% depending on site; all P < 0.05), The most consistent act ivity association was with vigorous activity in the previous 2 weeks (diffe rence between any vigorous activity versus none 22-25% greater; all P < 0.0 5), Conclusion. Sex- and joint compartment-related differences in cartilage dev elopment may be one explanation for variations in the pattern of knee OA se en in later life. Furthermore, the physical activity associations suggest t hat cartilage development is amenable to modification.