Factors influencing good knee joint range of motion and pain-free recovery 2 years after total knee arthroplasty.

Abstract

We investigated the factors associated with achieving a flexion angle of at least 120° and a numerical rating scale (NRS) score of 1.0 or less (maximum 0, minimum 10) 2 years after cruciate retaining-total knee arthroplasty (CR-TKA). We retrospectively studied 100 consecutive patients that underwent CR-TKA in July 2018-December 2021 and divided them into two groups: those that achieved at least 120° flexion and 1.0 or less NRS at 2 years postoperatively (group G) and those that did not (group NG). The endpoints were preoperative and 1-year postoperative NRS, preoperative and 1-year postoperative flexion range of motion (ROM), 2 years postoperative flexion ROM, and preoperative Oxford Knee Score (OKS). Univariate, logistic regression analyses determined items with significant differences that were then used in receiver operating characteristic (ROC) analysis to determine cut-off values. Group G showed a lower body mass index (24.6 ± 3.3 vs. 26.6 ± 4.0; P = 0.016), lower 1-year postoperative NRS (0.53 ± 0.99 vs. 2.0 ± 2.0; P < 0.001), and higher 1-year postoperative flexion ROM (125.3° ± 6.2° vs. 114.9° ± 10.9°; P < 0.001). Preoperative NRS and ROM did not differ between the groups. Multivariate analysis revealed that flexion ROM at 1 year (odds ratio [OR]: 1.17, 95 % confidence interval [CI]: 1.03-1.27; P < 0.001) and NRS at 1 year (OR: 0.49, 95 % CI: 0.29-0.83; P < 0.001) were significantly associated with achieving a postoperative flexion angle ≥120° and pain-free recovery. The ROC cut-off values were a flexion angle ≥125° and NRS ≤1.0 at 1 year postoperatively. Predictors of achieving a flexion angle of 120° or more and NRS 1.0 or less at 2 years after CR-TKA were good ROM and adequate pain relief 1 year postoperatively, regardless of preoperative pain or ROM.