Osteonecrosis is by restriction of osseous circulation that leads to necrosis of osseous tissue. The knee is the second most common site for osteonecrosis after the hip. Osteonecrosis of the knee may be spontaneous osteonecrosis or secondary osteonecrosis (related to several risk factors such as alcohol abuse, sickle cell disease, systemic lupus erythematosus, Gaucher disease, Fat Embolism). Spontaneous osteonecrosis involves only the medial femoral condyle whereas secondary osteonecrosis may affect both condyles.