Osteonecrosis (ON) of the knee is a progressive disease that often leads to subchondral collapse and disabling arthritis. Recent studies have identified three distinct pathologic entities, all of which were previously described as knee ON: secondary ON, spontaneous ON of the knee, and postarthroscopic ON. Radiographic and clinical assessment is useful for differentiating these conditions, predicting disease progression, and distinguishing these conditions from other knee pathologies. The etiology, pathology, and pathogenesis of secondary ON of the knee are similar to those found at other sites (eg, hip, shoulder). Spontaneous ON is a disorder of unknown etiology. Postarthroscopic ON has been described as an infrequent but potentially destructive complication. Various treatment modalities (eg, core decompression, bone grafting, high tibial osteotomy, arthroplasty), have been used with varying degrees of success for each type of ON. Secondary ON frequently progresses to endstage disease, and early surgical intervention is recommended. Initial management of spontaneous ON of the knee and postarthroscopic ON is typically nonsurgical, with observation for clinical or radiographic progression.
From the Department of Orthopedic Surgery, Sinai Hospital, Baltimore, MD (Dr. Mont and Dr. Zywiel), and the Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore (Mr. Marker and Dr. Carrino).
Dr. Mont or an immediate family member has received royalties from Stryker; serves as a paid consultant to or is an employee of Stryker and Wright Medical Technology; and has received research or institutional support from the National Institutes of Health (NIAMS and NICHD), Stryker, Tissue Gene, Joint Active Systems, Salient Surgical Technologies, and Wright Medical Technology. Dr. Carrino or an immediate family member serves as a paid consultant to Quality Medical Management and Medtronic; serves as an unpaid consultant to GE Healthcare, Carestream Health, and Siemens Medical Systems; and has received research or institutional support from Siemens Medical Systems, Carestream Health, and Toshiba Medical. Neither of the following authors nor any immediate family member has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Mr. Marker and Dr. Zywiel.