Secondary Osteonecrosis of the Knee

Excerpt

Secondary osteonecrosis of the knee (SON) is a subtype of avascular necrosis that affects the subchondral bone of the knee joint and can lead to progressive bone collapse and end-stage osteoarthritis. Osteonecrosis in the knee was first described by Ahlbäck in 1968 and is now recognized to encompass 3 distinct entities: primary (spontaneous or idiopathic) osteonecrosis of the knee (SONK), which occurs without identifiable risk factors; SON, which is associated with predisposing conditions; and post-arthroscopic osteonecrosis, which can occur after knee arthroscopy.

Secondary osteonecrosis typically affects a younger population (eg, those aged 50 or younger). This condition often involves multiple foci or joints, unlike SONK, which usually affects older adults and is limited to a single lesion. Patients with SON frequently have identifiable risk factors (eg, corticosteroid use or alcohol abuse) and may present with bilateral knee involvement or concurrent osteonecrosis in other joints, especially the hips. Without prompt diagnosis and appropriate management, SON can progress to subchondral bone collapse, joint cartilage destruction, and debilitating arthritis requiring total knee arthroplasty. Therefore, early recognition and intervention are critical to preserve the native joint and delay or prevent the need for joint replacement. This activity reviews SON's etiology, clinical presentation, evaluation, staging, and management, emphasizing the current standard of care and surgical treatment outcomes, and discusses emerging therapies. This activity aims to provide the learner with an updated, evidence-based overview of how orthopedic specialists manage this challenging condition.