Major complication following minor outpatient procedure: osteonecrosis of the knee after intraarticular injection of cortisone for treatment of knee arthritis.

This report describes an 80-year-old woman who underwent intraarticular steroid treatment for her arthritic knee and ended up with avascular necrosis of her medial femoral condyle. This rare complication should alert all clinicians that even minor procedures such as arthrocentesis may result in complications.