ICD-10 Code G57.90 – Unspecified mononeuropathy of unspecified lower limb (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G57.90 – Unspecified mononeuropathy of unspecified lower limb
What it is
Use this code for a single peripheral nerve disorder affecting a lower limb when the record does not identify the exact nerve or side. It signals mononeuropathy, but the documentation remains nonspecific.
Clinical signs
Typical findings include localized numbness, tingling, pain, weakness, or sensory loss in one lower extremity nerve distribution. Clinical features vary; refer to documentation.
When to use this code
Assign G57.90 when the clinician documents mononeuropathy of the lower limb without naming the affected nerve or laterality. Use it when the chart supports a single-nerve process, but details are incomplete.
If the note only says neuropathy, paresthesia, or leg pain without confirming mononeuropathy, check documentation before coding. This code is appropriate for unspecified lower-limb nerve involvement, not for broader polyneuropathy.
Do not use for
Do not use this code for polyneuropathy, radiculopathy, or a clearly named mononeuropathy of a specific nerve. Check documentation if the side or nerve is identified.
Coding tip
Query for the exact nerve and laterality whenever possible, because a more specific code may be available.