Although knee malalignment is a risk factor for the progression of unicompartmental knee osteoarthritis (OA), it is unclear how this relationship is mediated. Cartilage defects are known to predate cartilage loss and the onset of knee OA, and it may be that knee malalignment increases the risk of unicompartmental knee cartilage defects. Knee radiographs and MRI were performed on a total of 202 subjects, 36.6% of whom had radiographic knee OA, to determine the relationship between static knee alignment and knee cartilage defects. Analyses were performed for the entire cohort, as well as for healthy and OA subgroups. For every 18 increase in a valgus direction, there was an associated reduced risk of the presence of cartilage defects in the medial compartment of subjects with knee OA (p ¼ 0.02), healthy subjects (p ¼ 0.002), and the combined (p < 0.001) group. Moreover, for every 18 increase in a valgus direction, there was an associated increased risk of the presence of lateral cartilage defects in the OA group (p ¼ 0.006), although the relationship between change toward genu valgum and lateral compartment cartilage defects did not persist for the healthy group (p ¼ 0.16). This cross-sectional study has demonstrated that knee alignment is associated with the risk for compartment specific knee cartilage defects in both healthy and arthritic people. Given that the natural history of cartilage volume reduction appears to be predated by the presence of cartilage defects, whether knee alignment affects the longitudinal progression from cartilage defects to cartilage loss requires further examination. ß

This study has demonstrated that the static knee angle, measured as a continuous variable, is an important determinant of the compartment-specific features of radiographic knee OA. Further work is required to determine whether interventions aimed at correcting these relatively minor levels of varus and valgus angulation will have an effect on the risk of tibiofemoral OA.

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