Heart Attack After Total Knee Replacement Bruce Jancin writing in rheumatology News reported on a British study of more than 13,000 patients who underwent total knee replacement. A matched nonsurgical group was used as control. During the first month after knee replacement, there was an almost 9 fold increase in the risk of heart attack compared with the control group. At 3 months the risk was four times greater and at 6 months 2 times greater. Another finding was that the risk of venous thromboembolism- a blood clot that goes to the lungs- remained elevated for 5 years.