Treatment of osteonecrosis of the knee

The term osteonecrosis encompass three different disorders with different symptoms, aetiologies and characteristics: spontaneous, secondary, and post-arthroscopic osteonecrosis of the knee. These three entities have non-specific symptoms and radiological findings at early phases but all have the potential of progress to late stage disabling joint disease with different rates. Clinical assessment and radiographic findings are useful for differentiating these three entities from other conditions with similar onsets. Different treatment modalities have been used (e.g., core decompression, bone grafting, vascularized free fibula transfer, high tibial osteotomy, arthroplasty) with varying success for each type and stage. While spontaneous and post-arthroscopic osteonecrosis have a higher potential to regress, secondary osteonecrosis generally leads to end-stage disease with multiple joint involvement. The term osteonecrosis (ON) was firstly described by Ahlbäck et al. as “a radiolucent lesion in the medial femoral condyle” in 1968 (Ahlbäck et al., Arthritis Rheum 11:705–733, 1968). Preliminary studies characterized this entity as a late onset disorder with a greater prevalence in women. Later studies reported three different conditions encompassed by ON with different symptoms, aetiologies, age of onset and characteristics: spontaneous osteonecrosis of the knee, secondary osteonecrosis of the knee, and post-arthroscopic osteonecrosis of the knee (Mankin, N Engl J Med 326:1473–1479, 1992; Pape et al., Arthroscopy 23:428–438, 2007). Because of the risk of progress to end-stage osteoarthritis, clinicians should identify and manage the disease for optimal outcomes. Diagnosis, classification and management of these disorders are still controversial because of the low number of comparative prospective studies and low incidence. Current opinions about aetiology, diagnosis and treatment of osteonecrosis of the knee addressing each sub-type separately are reviewed here.