Foot posture as a biomechanical outcome measure following total knee arthroplasty in individuals with severe knee osteoarthritis

Total knee arthroplasty (TKA) is commonly performed to relieve pain and improve knee function in individuals with severe knee osteoarthritis (OA). Abnormal foot mechanics can influence overall biomechanics and affect post-surgical outcomes. This study aimed to evaluate foot posture as a biomechanical outcome before and after TKA and to explore its relationship with pain, functional performance, and quadriceps (Q) angle. Seventy-seven individuals with knee OA who underwent TKA, and 77 healthy controls were assessed. Foot posture was measured using the Foot Posture Index (FPI), pain using the Numerical Pain Rating Scale (NPRS), and function using the Lower Extremity Functional Scale (LEFS), Timed Up and Go (TUG), and 6-Minute Walk Test (6MWT). Q-angle was assessed as a structural alignment measure. Evaluations were conducted preoperatively and at 6 weeks, 3, 6, and 12 months postoperatively. Preoperative FPI was significantly higher in the OA group than controls (1.52 ± 2.5 vs. 0.70 ± 2.2; p = 0.03). At 6 months post-TKA, FPI remained higher than controls (p = 0.03), but the difference from controls was no longer statistically significant at 12 months. A weak correlation existed between FPI and pain (p < 0.05); no correlation was found with functional or alignment outcomes. Foot posture provides limited longitudinal insight; broader biomechanical assessment is advised.