The goal of this observational study is to compare the functional outcome of patients with end-stage knee osteoarthritis (OA) before and after total knee arthroplasty based on the phase angle level. The main questions it aims to answer are: * Do patients with low phase angle show worse functional recovery after total knee arthroplasty compared to those with high phase angle? * Is postoperative physical function associated with preoperative phase angle level? Researchers will compare postoperative physical function and muscle strength between the low and high phase angle groups to determine whether a low phase angle is associated with poorer functional recovery. Participants will: Perform physical function tests, isokinetic strength assessments, and bioelectrical impedance analysis before and three months after surgery.