In 2016, the Center for Medicare and Medicaid Innovation (CMMI) launched the Comprehensive Care for Joint Replacement (CJR) program, a pilot evaluation of 90-day episode payments for lower-extremity joint replacements (LEJR).1 Under the CJR model, a 5-year program, participating hospitals receive bundled payments for knee and hip replacements that subsume the index hospitalization and all spending for 90 days following this index hospital stay. Participation in the CJR program was initially mandatory for approximately 800 acute care hospitals in 67 metropolitan statistical areas (MSAs) that were not already enrolled in the Bundled Payment for Care Improvement (BPCI) initiative, an ongoing voluntary bundled payment pilot program also overseen by CMMI. Policymakers hoped that holding hospitals financially accountable for all Medicare spending during the bundle window would incentivize these facilities to collaborate with outpatient clinicians and postacute care (PAC) facilities to improve care quality, coordination, and value. In 2018, CMMI made participation in the CJR program voluntary for hospitals in 33 of the 67 original MSAs.