Osteonecrosis of the knee: a review of three disorders.

Osteonecrosis of the knee is a debilitating disease that is poorly understood. Originally described as a single disorder, it encompasses three distinct conditions: spontaneous osteonecrosis of the knee (SPONK), secondary osteonecrosis of the knee, and post-arthroscopic osteonecrosis of the knee. This article reviews the current knowledge of these distinct conditions by describing their etiology, pathology, and pathogenesis, as well as their clinical and radiographic presentations. The various treatment options available for each condition are reviewed, with a discussion of their rationale and indications, and a summary of results with various techniques. A thorough understanding of these conditions and their distinguishing features is critical to selecting the best treatment option for an individual patient.