ObjectiveTo study the effect of the Comprehensive Care for Joint Replacement (CJR) bundled payment program on postoperative home health and outpatient physical therapy (PT) for total hip or knee arthroplasty (THA/TKA). DesignRetrospective cohort with national Medicare data (5% claims) using a difference-in-differences analysis comparing January 2013-September 2015 (before) versus October 2016-September 2019 (after). SettingAdministrative claims from hospitals in 34 metropolitan statistical areas with mandatory CJR participation as of 2018 and 42 control metropolitan statistical areas. ParticipantsEpisodes in fee-for-service Medicare beneficiaries (5% claims) undergoing elective THA (n=6327) or TKA (n=10,764) with community discharge. InterventionsImplementation of CJR bundled payment program. Main Outcome MeasuresHome health and outpatient PT, including any use and number of visits. ResultsProgram implementation was associated with an increased percentage of THA episodes using home health PT (+8.0 percentage-point change; 95% CI, +3.5 to +12.6; P=.001) but a decreased per-episode number of home health PT visits for THA (−1.1; 95% CI, −1.6 to −0.6; P<.001) and TKA (−1.1; 95% CI, −1.4 to −0.7; P<.001). The program was also associated with an increased per-episode number of outpatient PT visits for TKA in the primary but not sensitivity analyses (+0.8; 95% CI, +0.1 to +1.4; P=.02). ConclusionsFindings of increased home health PT may reflect an intentional shift in care from the inpatient postacute setting to the community to decrease costs. Alternatively, the limited effect of CJR, particularly on outpatient PT, could reflect challenges with care coordination in a retrospective bundle spanning multiple care settings.