The purpose of the study: is to quantify the amount of post-operative effusion or hematoma present after total knee arthroplasty pre-operatively, post-operative day #0,1. Patients undergoing a total knee arthroplasty will undergo an MRI on the operative knee at the following times: * Pre-operatively * Post-operative day #1 (approximately 16-20 hours post op) * Post-operative day #2 (approximately 36-40 hours post op) This will be conducted by the Loma Linda radiology department as per normal protocols. No special imaging procedures will be undertaken. Subjects will be both male and females, they will be patients from the Principle Investigator and Co-Investigators practice. Subjects will be between the ages of 18-89 years of age. The total participation will last approximately 30 days. Subject selection will be approximately 10 English speaking, both male and female between the ages of 18 to 89 years of age. Subjects will be recruited from the Principal Investigators and Co-Investigators clinic. There will be no advertising or electronic recruiting. The study is expected to last 12 months.