Secondary Osteonecrosis of the Knee

Osteonecrosis (ON) is a degenerative condition of the bone in which the cellular component dies secondary to an interruption of the blood supply. This clinical entity was first described in 1968 by Ahlback et al. Now osteonecrosis of the knee describes three distinct disorders which can be clearly distinguished: primary or spontaneous osteonecrosis, secondary osteonecrosis, and post-arthroscopic osteonecrosis of the knee.Spontaneous osteonecrosis of the knee (SPONK) has been discussed most in the literature but is the least understood, and its etiology is still unclear. The insidious and often non-specific onset of SPONK leads to difficulties in diagnosis and, therefore, prompt treatment. Advanced disease of all three subtypes of ON leads to subchondral collapse, end-stage osteoarthritis, and the requirement for surgical intervention. In this article, we will review the current etiology, diagnosis, and treatment of secondary osteonecrosis of the knee (SON).