A new study found that the number of total knee replacements performed on Medicare patients has more than doubled between 1991 and 2010. Total knee arthroplasty (TKA) procedures are both highly effective at relieving symptoms of severe knee arthritis and expensive. Approximately 600,000 TKA procedures are performed annually in the US, and each procedure costs approximately $15,000. That adds up to $9 billion per year. The study’s authors examined Medicare Provider Analysis and Review (MedPAR) for the time period to determine changes in TKA volume, per capita utilization, hospital length of stay (LOS), readmission rates, and adverse outcomes. The authors say it is difficult to determine whether the increase in TKAs is because more patients are showing symptoms that warrant the procedure or if doctors are interested in the high reimbursement. Because there is no national joint arthroplasty registry, it is difficult to determine the appropriateness of the procedures; however, a Spanish study estimated that as many as 25% of TKA procedures performed in that country were considered inappropriate. In the end, the authors conclude it is likely a combination of the two factors. It is interesting to note that the average LOS for patients who undergo TKA has fallen. Authors believe this trend is due to the Medicare prospective payment system which provides hospitals a financial incentive to discharge patients early. However, the data also shows an increase in the number of readmissions associated with TKA procedures which suggests patients are being discharged too soon.