Functional activities and patient satisfaction after total knee arthroplasty for valgus knee are inferior to those for varus knee: A propensity-matched cohort study

Abstract

Background: This study aimed to compare the clinical outcomes of total knee arthroplasty (TKA) for valgus and varus knees in a background-matched cohort.

Method: Preoperative and two years postoperative original and new Knee Society Scores (OKSS and 2011KSS, respectively) were obtained from patients who underwent primary TKA. Propensity score-matched cohorts were assessed for valgus and varus knees with malalignment ≥3°, ensuring parity in age, sex, primary diagnosis, body mass index, deviation from neutral alignment, surgical approach, patellar resurfacing, and implant type. Multiple linear regression analysis was performed on the 2011KSS Functional activities.

Results: Of the 1158 TKAs involving 122 valgus, 110 neutral, and 924 varus knees, propensity score matching yielded 106 valgus-varus knee pairs. Preoperatively, both groups exhibited similar scores, except for 2011KSS expectations. At two years, valgus knee showed inferior OKSS Function Score (valgus: 69.5 ± 26.7, varus: 79.6 ± 19.3, P = 0.005) and 2011KSS Functional activities (valgus: 57.8 ± 23.3, varus: 66.9 ± 20.4, P = 0.007) to varus knees. Valgus knees also showed inferior 2011KSS Satisfaction at two years (valgus: 25.1 ± 7.8, varus: 28.5 ± 7.8, P = 0.006). In the multiple linear regression analysis, older age, preoperative valgus deformity, rheumatoid arthritis, higher BMI, and lower functional scores were significant independent variables that predicted lower 2011KSS Functional activities (R² = 0.28).

Conclusion: Postoperative clinical scores related to function after TKA were inferior in valgus knees to varus knees in the background-matched comparison. Valgus knees carry the risk of limited postoperative function after TKA.

Keywords: Alignment; Osteoarthritis; Patient-reported outcome measures; Total knee arthroplasty; Valgus knee.