Fibrous dysplasia (monostotic), unspecified ankle and foot

This code signifies a benign, localized bone disorder characterized by the replacement of normal bone with fibrous tissue and immature woven bone, affecting a single bone in the ankle or foot region. It represents a developmental anomaly of bone formation rather than a neoplastic process.

Use this code for documented cases of monostotic fibrous dysplasia specifically located in an unspecified bone of the ankle or foot. Supporting documentation should clearly indicate the diagnosis and the affected anatomical region, without specifying laterality.

• Ensure the documentation explicitly states "monostotic" and specifies the ankle or foot as the affected site.
• Avoid using this code if the laterality (right or left) of the ankle or foot is known; instead, use the more specific codes M85.071, M85.072, or M85.073.
• Do not confuse with polyostotic fibrous dysplasia (M85.08) or other bone dysplasias.