Background Although total knee arthroplasty (TKA) has gradually become an effective treatment for osteoarthritis (OA) of the knee in the elderly, there is insufficient information on the relationship between the advantages and disadvantages of TKA and the cost-effectiveness ratio of TKA in the treatment of knee OA. For these reasons, LovaldST et al. conducted a controlled study to investigate whether there are differences in the associated medical costs and post-treatment functional status between patients with and without TKA for knee OA. METHODS Sample data from 1997 through 2009 were selected from the US Medicare database, and a 5% sample size of cases with ICD-9 code 715.X6 was randomly selected for the study. The selected OA cases were divided into non-TKA and TKA groups. Evaluation metrics included average annual treatment expenditures corrected for January 2011 exchange rates, mortality, newly diagnosed congestive heart failure, diabetes mellitus, and psychiatric depression. Differences in spending and hazard ratios between the two groups for each of the evaluated metrics were determined by regression analysis based on age, gender, race, patient agreement with treatment, patient’s region of residence, and Charlson score values. Corresponding results were comparatively analyzed at 1, 3, 5, and 7 years postoperatively. RESULTS There were 80,629 non-TKA and 53,829 TKA cases at 1-year postoperative follow-up, and the corresponding values at 7 years postoperatively were 39,183 and 25,904 cases, respectively. The total cost for patients in the non-TKA and TKA groups for the treatment of knee OA at 7 years postoperatively was$63,940 and$83,783, respectively, with the total cost in the TKA group being$19,843 more than in the non-TKA group over the 7-year period. DISCUSSION AND CONCLUSIONS Although this study showed that the 7-year postoperative cumulative cost was$19,843 higher in patients with knee OA treated with TKA than in the non-TKA group, the study did not account for the cost of medications in calculating the cost, which has been reported to be significantly higher in patients who did not undergo TKA than in patients who received TKA therapy. The risk of death for cases in the TKA group during the study’s 7-year follow-up period was about half that of the non-TKA group. The conclusions of this study indicate that TKA surgery significantly reduces mortality in patients with knee OA without significantly increasing long-term medical costs. Notably, cases in the TKA group were more likely to experience psychiatric depression during the first 3 postoperative years than those in the non-TKA group, suggesting that attention should be paid to monitoring the mental health status of this group of patients and intervening medically when necessary.