Hospitals that left the Comprehensive Care for Joint Replacement program this year treated more medically complex and Medicaid patients and had lower joint-replacement volumes, according to a study published online this week in JAMA Internal Medicine. The Centers for Medicare & Medicaid Services launched the five-year bundled payment pilot in 2016, initially making participation mandatory for about 800 acute care hospitals in 67 metropolitan statistical areas. When the program this year became voluntary for hospitals in 33 of the MSAs with the lowest historical costs, nearly three-quarters of the 205 hospitals that could leave the program did so. “Hospitals with a higher proportion of socially vulnerable patients might be more likely to leave the program because episode spending for these patients tends to be high owing to greater complication rates and more common use of institutional post-acute care,” the authors said. “The CJR program cost thresholds are more restrictive for hospitals with historical costs higher than regional average rates because the threshold is a weighted average of each hospital’s historical and regional costs in the first three years of the program and will be entirely based on regional costs starting in 2019.”