Shih-Yin Chen,1 Ning Wu,1 Yuan-Chi Lee,1 Yang Zhao21Health Economics and Epidemiology, Evidera, Lexington, Massachusetts, 2Health Economics and Outcomes Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey, USAPurpose: The aim of the study reported here was to examine health care resource utilization, costs, and risk of rehospitalization for total knee replacement (TKR) patients with and without muscle atrophy/weakness (MAW).Patients and methods: Individuals aged 50–64 years with commercial insurance or 65+ years with Medicare Supplemental Insurance (Medicare) who had a hospitalization for TKR between January 1, 2006 and September 30, 2009 were identified from a large US claims database. First hospitalization for TKR was defined as the index stay. All patients were classified into three cohorts according to when MAW was diagnosed relative to TKR: pre-MAW, post-MAW, and no MAW. The association between MAW and health care costs over the 12-month post-index period and the probability of rehospitalization were assessed via multivariate regressions.Results: The study sample included 53,696 Medicare and 46,058 commercial insurance TKR patients. Controlling for cross-cohort differences, both the pre- and post-MAW cohorts had significantly higher total health care costs (Medicare US$4,201 and US$9,404 higher, commercial insurance US$2,737 and US$6,640 higher, respectively) than the no MAW cohort (all P < 0.05). The post-MAW cohort in both populations was also more likely to have any all-cause or replacement-related rehospitalization compared with the no MAW cohort.Conclusion: Among US patients undergoing TKR, those with MAW had higher health care utilization and costs than patients without MAW.Keywords: rehospitalization, resource utilization, Medicare, health insurance, USA