ICD-10 Code G57.9 – Unspecified mononeuropathy of lower limb (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G57.9 – Unspecified mononeuropathy of lower limb
What it is
This code identifies a single-nerve disorder affecting the lower limb when the exact nerve is not documented. Use it when the record supports mononeuropathy, but the provider does not specify the site or type.
Clinical signs
Findings may include localized numbness, tingling, pain, or weakness in one lower-extremity nerve distribution. Clinical features vary; refer to documentation for the affected nerve and whether the neuropathy is compressive, traumatic, or idiopathic.
When to use this code
Use G57.9 when the provider documents mononeuropathy of the leg or foot without naming a specific nerve. It also fits cases where the note confirms a lower-limb nerve disorder, but the available record does not support a more specific code. If later documentation identifies the nerve, code to the more specific category instead.
Do not use for
Do not use this code for polyneuropathy, radiculopathy, or generalized peripheral neuropathy. Check documentation if the record names a specific lower-limb nerve or another neurologic cause.
Coding tip
Query for the exact nerve involved before defaulting to the unspecified code.