Adverse events from 2033 total knee arthroplasty patients were documented by nonphysician abstractors. The annual rate of adverse events from 2002 to 2004 was 9.2%, 6.4%, and 5.8%, respectively. Congestive heart failure (odds ratio, 2.1; 95% confidence interval, 1.2-3.5; P < .01) and chronic obstructive pulmonary disease (odds ratio, 1.8; 95% confidence interval, 1.2-2.7; P < .01) were associated with a significantly increased risk of experiencing any adverse event during the index hospitalization. The 30-day postprocedure rate of readmission for all causes was 5.5%. Experiencing an adverse event during the index hospitalization increased the length of stay (P < .001). The rate of symptomatic venous thromboembolism 30 days postprocedure was 1.7%. The 30-day postprocedure mortality rate was 0.3%. Experiencing any adverse event was associated with an increased 30-day postprocedure mortality (P < .001). Compared with previous studies of Medicare claims, these data reveal a substantial decrease in the mortality rate, an increased readmission rate, and no substantial change in the rate of venous thromboembolism.