Osteonecrosis of the knee

Osteonecrosis of the knee is a degenerative syndrome characterized by osseous necrosis of a load-bearing portion of the distal femur or proximal tibia, followed by subchondral insufficient fractures, subsequent segmental collapse and osteoarthritis which may require surgical intervention. It can be divided into three clinical entities with different etiologies: spontaneous osteonecrosis of the knee (SPONK), secondary osteonecrosis of the knee (SON) and post-surgical osteonecrosis of the knee (ONPK). The knee is the second articulation involved in terms of frequency by osteonecrosis; the spontaneous or idiopathic form is the most common clinical findings. The secondary form is caused usually by prolonged steroid therapy used for many pathologies such as systemic lupus erythematosus chronic, bronchial asthma and autoimmune arthritis. The third form, ONPK, was first described as a post-arthroscopic complication but nowadays is considered more like a post-knee surgery complication. The management of this disease is conservative when possible, with a good percentage of patients responding to the therapy (especially spontaneous form) but it may require surgical intervention such as core decompression, high tibial osteotomy, unicompartimental knee replacement or total knee replacement. Osteonecrosis of the knee is a rare condition that orthopaedic surgeons must recognize and treat as soon as possible.