Impaired function of the multifidus muscles — the deep spinal stabilizers running along the lumbar vertebral column — resulting in reduced motor control, lumbar instability, pain, or weakness.

Documentation tips

What should appear in the chart to support M62.85.

Source · Editorial brief grounded in 6 cited references ↓

• Document 'multifidus dysfunction' or 'multifidus muscle dysfunction, lumbar' explicitly — vague terms like 'core weakness' or 'lumbar muscle dysfunction' won't map cleanly to M62.85.
• Include objective findings that support the diagnosis: MRI evidence of multifidus atrophy or fatty infiltration, EMG/physiological testing showing reduced multifidus activation, or clinical examination findings of segmental instability.
• Record the patient's history of conservative treatment failure (physical therapy, pain medications) if the encounter supports consideration of advanced interventions such as neurostimulation.
• Note whether the dysfunction is associated with a prior acute lumbar injury — documenting the mechanism (e.g., post-injury inhibition pattern) strengthens clinical specificity.
• If a comorbid condition is present (e.g., lumbar radiculopathy, degenerative disc disease), code both diagnoses and sequence according to the primary reason for the encounter.

Related CPT procedures

Procedure codes commonly billed with M62.85. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M62.85 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Using M54.5x (low back pain) instead of M62.85 when the provider has specifically diagnosed multifidus dysfunction — these are not interchangeable; M62.85 is the more specific code and should be used when documented.
• Conflating M62.85 with M62.81 (muscle weakness, generalized) — multifidus dysfunction is a site-specific, mechanism-driven diagnosis, not a generalized weakness code.
• Applying M62.85 to thoracic or cervical multifidus findings — the code is strictly lumbar region; there is no parallel code for other spinal regions in the current code set.
• Failing to capture MCC/CC comorbidities that would shift the encounter from DRG 558 to DRG 557 — always review the full problem list before finalizing the claim.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M62.8 (laterality / anatomic variants).