Contralateral Knee Alignment Parameters Have Limited Influence on Coronal Alignment Progression Compared With Ipsilateral Parameters in Patients With Knee Osteoarthritis

Abstract

Objective. To compare alignment parameters in bilateral lower extremities and evaluate the effect of contralateral limb on hip-knee-ankle angle (HKAA) longitudinally. Methods. Native bilateral lower extremities of 3,045 Korean patients with long-leg radiographs were followed for progression of knee osteoarthritis. Concordance rates of Functional Knee Phenotypes (FKPs) and Coronal Plane Alignment of the Knee (CPAK), the proportion of patients with identical bilateral subtypes, were assessed. Varus, neutral, and valgus alignments were defined as baseline HKAA <= 177 degrees, 177 degrees< HKAA <183 degrees, and HKAA >= 183 degrees, respectively. Multivariable linear regressions for follow-up HKAA were conducted. Results. Concordance rates for FKPs and CPAK were 41.6% (95% confidence interval: 39.9-43.4%) and 53.5% (51.7-55.2%), respectively, at baseline and 35.5% (33.8-37.2%) and 55.4% (53.7-57.2%) at a mean 4.0-year follow-up. Contralateral parameters, Kellgren-Lawrence grade (P = 0.005) in bilateral varus group, medial proximal tibial angle (MPTA) (P = 0.046) in ipsilateral varus-contralateral neutral group, MPTA, and mechanical lateral distal femoral angle in bilateral neutral (P < 0.001; P = 0.012, respectively) and valgus (P = 0.003; P = 0.004) groups, were associated with follow-up HKAA. However, their standardized beta values were smaller than ipsilateral values. Conclusion. Concordance rates of FKPs and CPAK between bilateral limbs were 41.6% and 53.5% at baseline, respectively. Contralateral parameters have limited influence on coronal alignment progression compared with ipsilateral parameters.