Magnetic Resonance Imaging (MRI) of the Extremities — CPB 0171 | AETNA Coverage Update

TL;DR: Aetna, a CVS Health company, modified CPB 0171 governing extremity MRI coverage, effective September 26, 2025. Billing teams submitting CPT codes 73218–73223 (upper extremity) and 73718–73723 (lower extremity) need to verify their documentation matches updated medical necessity criteria before claims go out.

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Quick-Reference Table

Field	Detail Copy
Payer	Aetna, a CVS Health company
Policy	Magnetic Resonance Imaging (MRI) of the Extremities
Policy Code	CPB 0171
Change Type	Modified
Effective Date	September 26, 2025
Impact Level	High
Specialties Affected	Orthopedics, Radiology, Podiatry, Oncology, Vascular Surgery
Key Action	Audit documentation for knee MRI orders to confirm they meet at least one of five listed medical necessity criteria before billing CPT 73721–73723

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Aetna Extremity MRI Coverage Criteria and Medical Necessity Requirements 2025

The Aetna extremity MRI coverage policy under CPB 0171 Aetna system covers a defined set of clinical indications. "Medically necessary" is not a loose standard here — Aetna lists five specific knee MRI criteria, and your documentation needs to match at least one of them. Vague orders citing "knee pain" won't hold up on review.

Here's what qualifies for knee MRI (CPT 73721, 73722, 73723) under this coverage policy:

Tumor detection, staging, or post-treatment evaluation. ICD-10 codes like C49.20–C49.22 (malignant connective tissue, lower limb) and D21.20–D21.22 (benign connective tissue, lower limb) anchor this indication. The documentation needs to reflect an active oncologic workup or follow-up — not just a history of cancer.

Persistent knee pain, swelling, or instability. This splits into two sub-tracks. For non-injury pain, the patient must have failed at least three weeks of conservative therapy. Aetna defines conservative therapy explicitly: rest, ice, compression, elevation, NSAIDs, crutches, and range-of-motion exercises. All of them in combination — not just ibuprofen for a week.

For injury-related pain, the bar is different. Multi-view x-rays must have ruled out a fracture or loose body, and the clinical picture must remain uncertain after that. Both conditions have to be true. Document the x-ray results and spell out why the clinical picture is still unclear.

True locking of the knee. This indication comes with a clinical definition you should paste into your documentation template. True locking is more than a momentary locking with the knee flexed. It's not the "catching" sensation many patients describe in extension. If the chart says "catching" and not "locking," Aetna can deny the claim. Your ordering providers need to know this distinction.

Suspected osteomyelitis or osteonecrosis. For bone infection, the clinical suspicion itself triggers coverage. For osteochondritis dissecans or osteonecrosis, there's an added requirement: the clinical picture — including x-rays — must not be confirmatory. If x-rays already establish the diagnosis, the MRI doesn't meet medical necessity under this policy.

Beyond the knee, CPB 0171 also covers MRI for several other indications. MRI for CLOVES syndrome diagnosis is covered. MRI for osteomyelitis in the foot is covered. MRI for Morton neuroma (ICD-10 G57.60–G57.63) is covered for pre-operative planning — but only after a symptomatic neuroma is identified on plain x-ray and non-surgical treatments have failed. Those treatments include metatarsal support, padded shoe inserts, and steroid or local anesthetic injections (CPT 64450). All three need to have been tried and failed before the MRI is billable.

Whole-body MRI for malignancy screening is covered specifically for patients with Li-Fraumeni syndrome. This is a narrow indication — don't apply it broadly to other hereditary cancer syndromes.

MRI-lymphangiography for peripheral lymphedema is covered when lymphedema is the suspected cause of peripheral edema and initial noninvasive studies — specifically ultrasound — have come back negative. The sequencing matters. Ultrasound first, MRI-lymphangiography second.

If you're unsure how these criteria map to your patient mix, loop in your compliance officer before September 26, 2025.

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Aetna Extremity MRI Exclusions and Non-Covered Indications

CPT 70554 and 70555 — functional MRI of the brain — are explicitly not covered for indications listed in CPB 0171. Those codes cover brain functional MRI, including neurofunctional testing. They don't belong in an extremity MRI claim, and submitting them under this policy will result in a claim denial.

The policy also excludes CPT 73721–73723 for fitting of prosthetics. The full code description in the policy notes this exclusion directly. If you're billing joint MRI of the lower extremity in the context of prosthetic fitting, that's not a covered indication under CPB 0171.

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Coverage Indications at a Glance

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Aetna Extremity MRI Billing Guidelines and Action Items 2025

These are direct steps your billing and clinical teams should take before the September 26, 2025 effective date.

Copy Action Items

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CPT, HCPCS, and ICD-10 Codes for Extremity MRI Under CPB 0171

Covered CPT Codes (When Selection Criteria Are Met)

Not Covered CPT Codes

Code	Type	Description	Reason Copy
70554	CPT	Magnetic resonance imaging, brain, functional MRI; including test selection and administration of neurofunctional testing	Not covered for indications listed in CPB 0171
70555	CPT	Magnetic resonance imaging, brain, functional MRI; requiring physician or psychologist administration of entire neurofunctional testing	Not covered for indications listed in CPB 0171

HCPCS Codes

Code	Type	Description Copy
L3030	HCPCS	Foot, insert, removable, formed to patient foot, each
L3050	HCPCS	Foot, arch support, removable, premolded, metatarsal, each

Key ICD-10-CM Diagnosis Codes

The full policy includes 267 ICD-10-CM codes. Review the complete code set at CPB 0171 on PayerPolicy.

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