Predictive factors for functional outcomes in patients receiving total knee arthroplasty

The global demographic shift toward an aging population has led to a surge in osteoarthritis, particularly knee osteoarthritis. Total knee arthroplasty (TKA) has become a prevalent intervention, yet a significant proportion of patients fail to regain optimal physical function post-surgery. Predictors of functional outcomes have been explored, but there is a need for comprehensive investigations considering factors such as sex, age, body mass index (BMI), Kellgren-Lawrence grade, knee range of motion (ROM), comorbidities, and pain. We retrospectively analyzed data from 86 patients who underwent unilateral TKA. The study assessed functional outcomes using knee ROM and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) scale at 4 time points (T0: pre-TKA, T1: discharge, T2: 3 months post-surgery, T3: 6 months post-surgery). Statistical analyses included chi-square tests, t tests, generalized estimating equations models, and multiple regression. This study included 86 patients undergoing unilateral TKA with a mean age of 73 years. Preoperative BMI was 27.6 kg/m2. Knee ROM decreased from 101.1 ± 18.3 degrees at T0 to 95.9 ± 6.8 degrees at T1. WOMAC score at T0 was 40.4 ± 19.5. There was a significant difference in WOMAC scores between T1 and T2 (P < .001), with no difference between T2 and T3 (P = .169). Age displayed a strong positive correlation with WOMAC scores at T0 (coefficient = 0.15, P < .001) and a moderate positive correlation at T1 (coefficient = 0.12, P < .01). Knee flexion ROM significantly influenced WOMAC scores at T1 (coefficient = -0.32, P < .001). Generalized estimating equations models highlighted the correlation of male, age, and knee ROM at discharge with postoperative outcomes. BMI did not provide additional explanatory power. This study underscores the significant role of knee ROM at discharge in predicting postoperative outcomes (coefficient = -0.4142, P = .019). Functional improvement tends to reach a plateau by the third month post-TKA. Early enhancement of knee flexion ROM predicts better functional outcomes at 3 and 6 months after surgery, emphasizing the critical window of opportunity for enhancing recovery during the initial postoperative phase.