Despite the lower prevalence of obesity (a known risk factor for osteoarthritis (OA)), the prevalence of lateral tibiofemoral OA is higher in Chinese communities compared with Caucasian communities. One potential explanation is the difference in knee alignment between the two populations. We measured various knee alignment indices among Chinese and Caucasians and assessed whether these indices were different between the two racial groups.
We selected participants from the Framingham Osteoarthritis Study (FOA) and the Beijing Osteoarthritis Study (BOA), all without knee OA (Kellgren & Lawrence grade <2). Bilateral, fully extended anteroposterior knee radiographs were measured for the following angles in both knees: the anatomic axis (AA), the condylar angle (CA), the tibial plateau angle and the condylar-plateau angle (CP). We compared the mean of each measurement between the two racial groups adjusting for age and body mass index using linear regression and stratified by sex.
The mean AA, CA and CP were significantly different in the BOA compared with the FOA. For women, the mean AA and CA were significantly more valgus in BOA subjects, while in men, the mean AA and CP were more valgus in BOA subjects.
There are significant differences in knee morphology between Chinese and Caucasian cohorts, which result in a more valgus alignment of the distal femur in Chinese. This would serve to shift the mechanical loading towards the lateral compartment, and provide a possible explanation why Chinese have a higher prevalence of lateral tibiofemoral OA.