Osteonecrosis of the patella: Imaging features

Osteonecrosis of the patella, although uncommon, has become important to re cognize because it can be a cause of pain in the knee. We describe the imag ing manifestations of nontraumatic osteonecrosis of the patella in seven cl inical cases. The lesions uniformly involved the superior aspect of the pat ella. Conventional radiography displayed increased radiodensity, subchondra l radiolucent areas, and typical demarcation line surrounding the ischemic region. MR imaging and bone scintigraphy demonstrated the characteristic fe atures of osteonecrosis. Recognition of the imaging findings of osteonecros is involving the patella can preclude misdiagnosis and may obviate unproduc tive invasive diagnostic procedures. (C) 2001 Elsevier Science Inc. All rig hts reserved.