This study aims to compare the effects of the medial parapatellar approach (MP) and the subvastus approach (SV) on postoperative clinical function in total knee arthroplasty (TKA). A total of 84 patients, who visit the Joint Surgery Department of Peking University Third Hospital and are diagnosed with end-stage knee osteoarthritis and require unilateral, primary total knee arthroplasty, will be recruited. The patients will be randomly assigned to two groups, with 42 patients in each group. TKA will be performed using the MP and SV approaches respectively. Postoperative data such as quadriceps muscle strength, the time of first unassisted straight leg raise (SLR), joint range of motion (ROM), KSS score, WOMAC score, SF-12 score, VAS score, and shear wave elastography (SWE) of the medial thigh muscle will be collected. The patients will be followed up for 2 years postoperatively to compare the short-term and long-term clinical functional outcomes of the two surgical approaches.