Novel ideas for the comprehensive evaluation of varus knee osteoarthritis: radiological measurements of the morphology of the lateral knee joint

BACKGROUND: The lateral anatomical and morphological characteristics of knees with varus knee osteoarthritis (OA) have not received sufficient attention. This study used several radiological parameters to describe the morphological characteristics of the lateral knee with OA to determine whether there are relationships between varus knee OA and parameters such as lateral plateau widening (LPW), proximal fibula curvature (PFC), and fibula height (FH). METHODS: The study retrospectively analyzed 1072 subjects who underwent standard radiography for diagnosing or evaluating symptomatic knee joint disease. The 163 Kellgren and Lawrence (K–L) grades 0 and I knees were categorized into the no-knee-OA group, and the 909 K–L grades II–IV knees were classified into the knee-OA group. Medial proximal tibial angle, joint line convergence angle, hip–knee–ankle angle, LPW, PFC, and FH were measured. T tests and chi-square tests were used to compare each index between the two groups. Binary logistic regression was performed to examine the correlation between indexes and knee OA occurrence. Ordinal logistic analysis, principal component analysis, and multivariable linear regression analysis were performed to examine the correlations between the three lateral parameters and K–L grades and the degree of varus deformity. RESULTS: LPW and PFC were significantly greater and FH was significantly smaller in the knee-OA group than in the no-knee-OA group. LPW, PFC, and FH were correlated with knee OA occurrence. One principal component, named the comprehensive principal component score of varus deformity, was extracted from the three indexes, and the total variance of the principal component interpretation was 76.60%. Ordinal logistics and multivariable linear regression analysis showed that, after adjusting for age and BMI, LPW and PFC were positively correlated with K–L grading and varus deformity. FH was significantly and negatively correlated with K–L grading and varus deformity (all P < 0.05). CONCLUSIONS: Regular morphological changes take place in the lateral knee with varus OA, including lateral dislocation of the tibial plateau, proximal fibula bending, and upward movement of the fibular head. Changes in LPW, PFC, and FH could enable a more comprehensive assessment of varus knee OA occurrence, severity, and deformity. Level of evidence Retrospective Study Level III.