This study examines longitudinal trends in volume, utilization, and outcomes for primary and revision total knee arthroplasty (TKA) among Medicare beneficiaries from 1991 to 2010. The study analyzed data from Medicare Part A files, identifying 3,271,851 patients who underwent primary TKA and 318,563 who underwent revision TKA. The results show a significant increase in TKA volume, with primary TKA volume increasing by 161.5% and revision TKA volume increasing by 105.9% over the study period. Per-capita utilization also increased, with primary TKA utilization rising by 99.2% and revision TKA utilization by 56.8%. For primary TKA, the average hospital length of stay (LOS) decreased from 7.9 days in 1991–1994 to 3.5 days in 2007–2010, while the rate of 30-day readmission increased from 4.2% to 5.0%. For revision TKA, the LOS decreased from 8.9 days to 5.0 days, but the 30-day readmission rate increased from 6.1% to 8.9%, and the rate of wound infections increased from 1.4% to 3.0%. These findings suggest that while TKA volume and utilization have increased, there has been a corresponding rise in hospital readmission rates and complications, particularly in revision TKA. The study also found that the increase in TKA volume has been largely driven by increases in per-capita utilization. Additionally, the decrease in hospital LOS was accompanied by an increase in hospital readmission rates. The study highlights the need for further research into the appropriateness of TKA procedures and the factors contributing to the rise in readmission rates and complications. The findings suggest that while TKA is a common and cost-effective procedure, there are concerns about overuse and the need for improved outcomes and reduced complications.This study examines longitudinal trends in volume, utilization, and outcomes for primary and revision total knee arthroplasty (TKA) among Medicare beneficiaries from 1991 to 2010. The study analyzed data from Medicare Part A files, identifying 3,271,851 patients who underwent primary TKA and 318,563 who underwent revision TKA. The results show a significant increase in TKA volume, with primary TKA volume increasing by 161.5% and revision TKA volume increasing by 105.9% over the study period. Per-capita utilization also increased, with primary TKA utilization rising by 99.2% and revision TKA utilization by 56.8%. For primary TKA, the average hospital length of stay (LOS) decreased from 7.9 days in 1991–1994 to 3.5 days in 2007–2010, while the rate of 30-day readmission increased from 4.2% to 5.0%. For revision TKA, the LOS decreased from 8.9 days to 5.0 days, but the 30-day readmission rate increased from 6.1% to 8.9%, and the rate of wound infections increased from 1.4% to 3.0%. These findings suggest that while TKA volume and utilization have increased, there has been a corresponding rise in hospital readmission rates and complications, particularly in revision TKA. The study also found that the increase in TKA volume has been largely driven by increases in per-capita utilization. Additionally, the decrease in hospital LOS was accompanied by an increase in hospital readmission rates. The study highlights the need for further research into the appropriateness of TKA procedures and the factors contributing to the rise in readmission rates and complications. The findings suggest that while TKA is a common and cost-effective procedure, there are concerns about overuse and the need for improved outcomes and reduced complications.