Osteonecrosis of the patella and prosthetic extrusion after total knee arthroplasty

We report the occurrence of painless patella avascular necrosis and spontaneous prosthetic extrusion after total knee arthroplasty with lateral retinacular release, a previously unreported complication. The resultant wound was debrided and closed without complication or loss of knee function. We elected not to remove the fragments in this case because the patient remained asymptomatic, and the remaining patella almost certainly will reabsorb completely. We advise clinicians to pay careful attention to patella viability and prosthetic loosening when assessing postoperative radiographs of total knee arthroplasty, especially with lateral retinacular release.