Disability from knee dysfunction has important implications on a patient's performance of simple day-to-day tasks, work-related duties, and leisure activities, including sports. Diagnostic imaging is of fundamental importance in the clinical evaluation of the patient with knee pain. The use of magnetic resonance imaging (MRI) for the assessment of knee pain and dysfunction has increased over the past few years as orthopedic surgeons and radiologists have familiarized themselves with the unique advantages of this modality. Magnetic resonance imaging provides a comprehensive evaluation of a wide spectrum of intra-articular and extra-articular pathologic conditions involving the knee. One of the most common indications for MRI of the knee is osteonecrosis. Osteonecrosis of the patella is unusual, and it is a well-documented cause of knee pain. After a brief overview of the anatomy of the patella, the diagnosis of osteonecrosis at this site by conventional radiography, MRI, and other imaging methods is focused on in this review.