Abstract.[Purpose] We investigated postoperative improvements in the knee joint function of 121 patients (17 males, 104 females) who received total knee arthroplasty (TKA). [Subjects and Methods] The evaluation criteria were: knee joint flexion range of motion, knee joint extension strength and flexion strength, pain in the knee joint, score on The Japanese Orthopedic Association knee criteria of "pain" and "ability to ascend and descend stairs", and 6-minute walking distance. The time points for the evaluations were: prior to surgery, at the time of discharge, 3 months postoperative, 6 months postoperative, and 1 year postoperative. In addition, the level of satisfaction 1 year after the operation was also assessed.[Results] In the results, 6-minute walking distance and ability to ascend and descend stairs were significantly better at 3 months postoperative than before surgery. Knee joint range of motion at 3 months postoperative had improved to its preoperative status, and was significantly improved at 1 year postoperative. Knee joint extension strength at 3 months postoperative had recovered to its preoperative status, and was significantly improved at 6 months postoperative. Knee joint pain was significantly ameliorated at the time of discharge compared to before surgery. Knee joint pain had completely disappeared in approximately 30% of patients by 1 year after surgery, and 90% of patients were satisfied with the results of their surgery. Nevertheless, many of the patients still complained of knee discomfort from TKA.[Conclusion] The results of this study show that knee joint pain was reduced at the time of discharge, and that 6-minute walking distance and ability to ascend and descend stairs were significantly improved at 3 months postoperative. Moreover, these results suggest that there are improvements in knee joint extension strength after 6 months, and in knee joint range of motion at 1 year postoperative. The results show that knee joint function after TKA improves over the year after surgery.

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