Idiopathic aseptic necrosis of unspecified ankle

This code signifies the death of bone tissue in an unspecified ankle joint due to a lack of blood supply, without an identifiable cause such as trauma or infection. This condition, also known as avascular necrosis or osteonecrosis, leads to bone collapse and subsequent arthritis.

Apply this code when documentation clearly indicates idiopathic osteonecrosis affecting an ankle, and the specific ankle (right or left) is not specified. This diagnosis is typically supported by imaging studies (e.g., MRI, X-ray) showing characteristic bone changes and a clinical history ruling out secondary causes.

• Ensure documentation explicitly states "idiopathic" or "aseptic" and "unspecified ankle."
• If the specific ankle is known (right or left), use the more specific codes M87.071 or M87.072.
• Do not use this code if a secondary cause (e.g., trauma, steroid use, sickle cell disease) is identified; instead, code the underlying cause and the appropriate secondary osteonecrosis code.