Longitudinal Study of Functional Performance and Quality of Life Following Total Knee Arthroplasty in Individuals with Advanced Knee Osteoarthritis

Background/Objectives: Knee osteoarthritis (OA) is a leading cause of pain, disability, and reduced quality of life (QoL). Although total knee arthroplasty (TKA) improves symptoms, patient-reported recovery may not parallel functional recovery. This study aimed to longitudinally characterize functional performance and QoL recovery following TKA and determine the extent to which postoperative functional performance and QoL approached that of healthy individuals. Methods: This prospective, longitudinal, single-centre study included individuals aged 50–80 years undergoing TKA and a healthy reference group. The primary outcomes were functional performance and QoL, assessed using the Lower Extremity Functional Scale (LEFS), 6-Minute Walk Test (6MWT), Timed Up and Go (TUG) test, Single Limb Stance (SLS) test, Stair Climb Test (SCT), Knee Injury and Osteoarthritis Outcome Score (KOOS), and Short Form-36 (SF-36). Pain intensity, assessed using the Numerical Pain Rating Scale (NPRS), was a secondary outcome. Data were analysed using independent-samples t-tests and linear mixed-effects models (p ≤ 0.05). Results: Postoperative assessments demonstrated significant improvements across all parameters of pain, function, and QoL (p < 0.001). Pain intensity decreased progressively over time, while functional performance improved significantly compared to preoperative levels. Although 12-month postoperative functional performance outcomes remained significantly different from those of healthy controls, disease-specific (KOOS) and general (SF-36) QoL scores showed substantial recovery. At 12 months, no statistically significant between-group differences were detected across the eight measured SF-36 domains, although this does not establish equivalence between the groups. Conclusions: TKA results in significant improvements in pain, functional ability, and QoL over one year. Despite substantial improvement in patient-reported outcomes, residual deficits in performance-based function persisted at 12 months. The findings indicate that patient-reported QoL and objective functional performance may follow different recovery trajectories, highlighting the importance of assessing both dimensions after TKA.