Other cyst of bone, unspecified ankle and foot

This code signifies the presence of a non-specific, fluid-filled or semi-solid sac within the bone structure of an unspecified ankle or foot. These cysts are typically benign and may be asymptomatic or cause localized pain, swelling, or tenderness. They are distinct from bone tumors or infectious processes.

Use this code when documentation indicates an "other" type of bone cyst in the ankle or foot, but the specific type of cyst (e.g., aneurysmal, unicameral) is not identified. This code is appropriate when the laterality (right or left) of the affected ankle or foot is not specified in the medical record. Documentation supporting its use includes imaging reports (X-ray, MRI) describing a bone cyst without further pathological classification.

• Avoid using this code if a more specific type of bone cyst (e.g., unicameral bone cyst, aneurysmal bone cyst) is documented; use the appropriate specific code instead.
• Ensure the documentation clearly states "unspecified ankle and foot" or lacks laterality and specific anatomical detail for the ankle/foot.
• If the laterality (right or left) is known, but the specific type of cyst is not, use the more specific laterality code (M85.671, M85.672).