(l) Severe osteoarthritis (OA): Aged knee OA accounts for the largest proportion of TKA. TKA can be considered in cases where the quality of life is significantly affected by impaired joint movement, where clinical symptoms cannot be improved by conservative treatment, and where standing radiographs indicate significant joint space narrowing and/or inversion, valgus, or flexion contracture deformity of the knee. Trans-tibial high osteotomy or single-stomp replacement may be considered for unicompartmental OA. (2) Advanced knee lesions in rheumatoid arthritis and ankylosing spondylitis: In advanced cases with joint deformity, there may be significant pain symptoms prior to joint fusion. Since the average age of the patients is younger than OA, the choice of TKA can avoid ankylosing fusion of the joint, significantly improve joint function and enhance the quality of life of the patients. At the same time, the expectations of such patients should not be too high due to periarticular soft tissue contracture and polyarticular lesions. It is worth emphasizing that pain alone is not an indication for surgery in TKA. (3) Traumatic arthritis: severe trauma involving the joint surface, such as cases of failure to repair the joint surface after a comminuted tibial plateau fracture that severely affects function; secondary osteoarthritis resulting from meniscal injury or resection, etc. (4) Non-infectious arthritis such as hemophilic arthropathy, psoriasis, and large osteoarthrosis resulting in knee pain and dysfunction. (5) Joint destruction following infectious arthritis can be a relative indication for TKA if no active infection is confirmed. (6) Cases in which good joint reconstruction cannot be obtained after resection of tumors involving the knee joint surface. In such cases, a special tumor prosthesis must be custom-made. In conclusion, the indications for total knee arthroplasty are broad, but the problems of postoperative infection, prosthesis wear, loosening, and multiple revisions after TKA have not been resolved. Therefore, it remains important to strictly control the indications for surgery and to fully consider the age of the patient undergoing TKA. Due to the feasibility of revision surgery in terms of prosthesis design and technique, age is no longer an absolute indication for total knee replacement, but TKA surgery in younger patients should still be considered as a condition for second-stage surgery.