Nexus letter guide · 5235, 5236, 5237, 5238, 5239, 5240, 5241, 5242, 5243

Nexus Letter for Lumbar Spine: What It Must Say

The medical opinion connecting Lumbar Spine (5235, 5236, 5237, 5238, 5239, 5240, 5241, 5242, 5243) to your service is the piece of the file a rater weighs most heavily. This is what that letter has to contain — and a complete, real example you can read before writing a word.

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Sample — Illustrative Specimen

Invented veteran · fictional sample provider · not a signed medical opinion

INDEPENDENT MEDICAL OPINION

Veteran: Samuel Okonkwo (invented veteran — illustrative sample)
Condition at issue: Obstructive Sleep Apnea (ICD-10 G47.33)
Service-connected condition relied upon: Chronic Sinusitis (ICD-10 J32.9)
Basis of claim: Secondary service connection under 38 C.F.R. §§ 3.303, 3.310
Opinion date: August 4, 2026

REASON FOR EVALUATION

This is an independent medical opinion prepared for the purpose of assisting in the determination of eligibility for veterans benefits. Its single question is a medical one: whether Mr. Okonkwo's obstructive sleep apnea is proximately due to, the result of, or aggravated beyond its natural progression by his service-connected chronic sinusitis. It is addressed to the C&P examiner and the VA rating official who will weigh it.

MEDICAL OPINION

It is my opinion that it is at least as likely as not (a 50 percent or greater probability) that Obstructive Sleep Apnea is proximately due to, the result of, or aggravated beyond its natural progression by the veteran's service-connected Chronic sinusitis (38 C.F.R. §§ 3.303, 3.310). In short: but for the veteran's service-connected Chronic sinusitis, Obstructive Sleep Apnea would not have occurred, or would not have progressed to its current severity.

Based on the history and records reviewed and the medical literature governing this condition, I opine that Obstructive Sleep Apnea (ICD-10 G47.33) is proximately due to, the result of, or aggravated by his service-connected Chronic sinusitis (ICD-10 J32.9), under 38 C.F.R. § 3.310. This claim is brought as secondary to Chronic sinusitis, established as service-connected in the veteran's VA claims file; the opinion below rests on that anchor. The mechanism connecting the two conditions — chronic nasal and sinonasal obstruction increasing upper-airway resistance and collapsibility during sleep — is well established in the peer-reviewed literature and applies directly to a claimant, like Mr. Okonkwo, whose sinonasal disease began in service and whose obstructive sleep apnea was later confirmed on polysomnography. My opinion accounts for the recognized non-service risk factors for this condition, none of which displaces the sinonasal pathway as at least an equal and materially contributing cause.

Read all 4,348 words — free

The published example letter — an invented veteran and a fictional sample provider.

Key facts

Rated under: 38 CFR Part 4, DC 5235-5243
Diagnostic codes: 5235, 5236, 5237, 5238, 5239, 5240, 5241, 5242, 5243
The standard: “At least as likely as not” — 50% or greater
Connection theories: Direct (§ 3.303)

The short answer

A back pain nexus letter is a medical opinion that your lower back condition is "at least as likely as not" caused by an injury or the physical demands of your service, or by a service-connected knee, hip, or ankle condition that changed your gait. It should name the diagnosis, such as lumbar strain, degenerative disc disease, or a herniated disc, tie it to something documented in service, and explain why ordinary age-related wear, the rater's first alternative, does not account for it. If you have nerve symptoms down a leg, the letter should say so: radiculopathy is rated separately from the spine.

What a nexus letter is

A nexus letter is a written medical opinion from a licensed clinician stating that a veteran’s condition is “at least as likely as not” (a 50 percent or greater probability) connected to their military service — or to a condition already service-connected. It is the bridge between a diagnosis and service connection: the VA has your diagnosis and your service records, and the nexus opinion is what ties them together with medical reasoning a rater can weigh.

The standard · 38 CFR § 3.102

“At least as likely as not”

The opinion does not have to be certain, or even “more likely than not.” A 50 percent or greater probability meets the standard; when the evidence is in approximate balance, the benefit of the doubt goes to the veteran.

What a Lumbar Spine nexus letter must contain

1
The diagnosis, by name and code
Lumbar Spine named as a current, documented diagnosis — the condition the VA rates under 38 CFR Part 4, DC 5235-5243 (5235, 5236, 5237, 5238, 5239, 5240, 5241, 5242, 5243). No diagnosis, no service connection: the opinion has to be about a condition that exists in your records.
2
The theory of connection
For most Lumbar Spine claims this is direct service connection under 38 C.F.R. § 3.303 — the letter connects the condition to an in-service event, injury, or exposure, and says so explicitly.
3
The magic words, used correctly
The opinion must be stated to the VA's own standard: "at least as likely as not (a 50 percent or greater probability)." Weaker hedges like "possibly" or "may be related" fail; the standard is a specific legal threshold, and letters that don't invoke it get discounted.
4
A rationale, not a conclusion
The most common fatal flaw is the conclusory letter — an opinion with no reasoning. A rater is instructed to weigh the rationale: what in the records supports the connection, what the medical literature says about the mechanism, and why known alternative causes don't displace it. For Lumbar Spine specifically: Goniometer measurements of flexion from treating provider.
5
A licensed clinician's signature and credentials
The letter is medical evidence only when a licensed clinician — opining within their specialty — reviews it, exercises independent judgment, and signs it with their credentials. VA Claim Commander drafts the letter from your records and your story; your clinician signs it. An unsigned draft is a draft.

What a rater looks for in a Lumbar Spine nexus letter

A named diagnosis with imaging
Lumbar strain, degenerative disc disease, degenerative arthritis, spinal stenosis, or a herniated disc, with the X-ray or MRI that shows it. "Low back pain" alone gives the rater less to connect.
The in-service event or loading
A documented injury (a fall, a vehicle accident, a lifting injury), or years of carrying heavy loads, jumping, or working in cramped spaces. Sick-call visits for back pain, profiles, and physical therapy in service are the anchor points.
An answer to "it's just age"
Disc degeneration is common with age, so the opinion has to explain why yours is more than that: an earlier onset than expected, changes concentrated at the level of a known injury, or symptoms documented from service forward.
Continuity after discharge
Chiropractic visits, prescriptions, missed work, or treatment notes after service that carry the problem forward. The letter should explain any gap rather than ignore it.
Nerve involvement noted
Pain, numbness, or weakness down a leg, reflex changes, or a nerve study. The spine formula's Note (1) says objective neurologic findings are rated separately, so the letter and the exam should capture them.

Direct service connection for Lumbar Spine

Most back claims are direct, under 38 C.F.R. § 3.303. When they are secondary, the usual route is a service-connected lower-extremity condition:

A documented back injury
A fall, a hard landing, a vehicle accident, or a lifting injury recorded at sick call or in a line-of-duty report.
Cumulative loading
Rucking, body armor, heavy lifting, jumps, and hours in vehicles or aircraft seats. The letter explains how that loading causes the degeneration you have, in your records.
Secondary to a knee, hip, or ankle
A service-connected leg condition that causes a limp or uneven gait can overload the lower back (38 C.F.R. § 3.310). The opinion should point to the gait change in your records.

Example back pain nexus letter wording

The opinion section of a back pain nexus letter, for an invented veteran. A real letter is written by the clinician about your records, and the facts in it have to be yours.

Sample — Illustrative Specimen

Invented veteran · not a real medical opinion · do not copy as your own

Opinion: It is my medical opinion that the veteran's lumbar degenerative disc disease at L4-L5 and L5-S1 is at least as likely as not (a 50 percent or greater probability) caused by the lifting injury documented in service and the repetitive heavy lifting of her duties as an aircraft mechanic.

Records reviewed: service treatment records, including the 2011 note documenting acute low back pain after lifting a wheel assembly, physical therapy that followed, and two later sick-call visits for back pain; the DD-214; post-service chiropractic and VA records; and the lumbar MRI of August 2025.

History: The veteran reports low back pain from the 2011 injury onward, managed with chiropractic care from 2014 and prescription medication from 2019. She was 24 at the time of the injury.

Rationale: Acute lifting injuries and repeated heavy lifting in flexed and twisted positions load the lower lumbar discs and are a recognized cause of disc injury and early degeneration. Degeneration of this degree at two levels at age 38 is more than would be expected from age alone, and it sits at the levels treated in service. I considered weight and post-service work: her weight is normal and her civilian work is office-based.

Conditions often claimed secondary to Lumbar Spine

Once Lumbar Spine is service-connected, conditions it causes or makes worse can be claimed under 38 C.F.R. § 3.310. Each one needs its own nexus opinion explaining that link.

Why nexus letters fail

Conclusory: an opinion with no rationale. The rater is told to weigh reasoning, and a bare “it’s related” weighs nothing.
Wrong standard: “may be related” or “possibly caused by” instead of “at least as likely as not.”
Ignores the other causes: a strong letter names the recognized non-service risk factors and explains why they don’t displace the service connection.
Outside the specialty: a clinician opining far from their field gets less weight than one whose practice covers the condition.
Unsigned: a draft nobody signed is not medical evidence — it is homework.

Who can write a Lumbar Spine nexus letter

Any licensed clinician qualified to give a medical opinion on Lumbar Spine: a physician, or another licensed clinician opining within their field. VA's test is whether the person is qualified by education, training, or experience (38 C.F.R. § 3.159(a)(1)). It does not have to be a VA doctor. Your own treating provider, who already knows your history, is often the strongest choice.

VA Claim Commander drafts the letter from your records and your own words, so your clinician starts from a complete draft; they review it, change what they disagree with, and sign only if it is their opinion.

If your own doctor won't write one, a licensed clinician through Commander Health can review your records and, only if the evidence supports it, write and sign a nexus letter for Lumbar Spine. It is a flat $500 that includes the records review, separate from any VA Claim Commander plan, and the clinician can decline if your records don't support an opinion.

Ask your own doctor: draft the request Commander Health nexus letter

Common questions

Do I need a nexus letter for a Lumbar Spine VA claim?

If service connection isn't already established for Lumbar Spine, a medical nexus opinion is usually the piece a rater weighs most heavily. It connects the diagnosis (5235, 5236, 5237, 5238, 5239, 5240, 5241, 5242, 5243) to your service — or to an already service-connected condition — using the "at least as likely as not" standard. Presumptive claims are the main exception.

What must a nexus letter for Lumbar Spine say?

Four things: the current diagnosis by name and diagnostic code; the connection theory (direct under 38 C.F.R. § 3.303, or secondary under § 3.310); the opinion stated to the "at least as likely as not (50 percent or greater probability)" standard; and a medical rationale grounded in your records and the medical literature — not a bare conclusion. It must be signed by a licensed clinician.

Who has to sign a nexus letter?

A licensed medical professional — a physician, or another clinician opining within their specialty (38 C.F.R. § 3.159(a)(1) asks for someone qualified by education, training, or experience). VA Claim Commander drafts the letter from your own records and story; a licensed clinician reviews, exercises independent judgment, and signs. An unsigned draft is not medical evidence. If your own doctor won't write one, a licensed clinician through Commander Health can review your records and, only if the evidence supports it, write and sign a nexus letter for Lumbar Spine. It is a flat $500 that includes the records review, separate from any VA Claim Commander plan, and the clinician can decline if your records don't support an opinion.

How does VA rate back conditions?

Under the General Rating Formula for Diseases and Injuries of the Spine in 38 C.F.R. § 4.71a: 10, 20, 40, 50, or 100 percent for the lower back, based mostly on forward bending. For example, forward flexion greater than 30 but not greater than 60 degrees is 20 percent, and 30 degrees or less is 40 percent. Muscle spasm or guarding severe enough to cause an abnormal gait or spinal contour is also 20 percent.

Is sciatica rated separately from my back?

Yes. Objective neurologic findings such as radiculopathy down a leg are rated separately under the nerve codes, in addition to the spine rating. The exam should record them, and the nexus letter can connect them to the spine condition.

Can my back be secondary to my knee?

It can be claimed under 38 C.F.R. § 3.310 when a service-connected knee changed the way you walk. The opinion should point to the limp or gait change in your records and explain how it loaded the lower back.

What if my service records don't mention my back?

The claim is harder but not impossible. Statements from people who saw the injury or your back problems in service count as lay evidence (38 C.F.R. § 3.159(a)(2)), and a clinician can weigh them along with your job duties and the pattern on imaging.

How the VA rates Lumbar Spine →Lumbar Spine research library →Lumbar spine: range of motion and rating levels →Radiculopathy secondary to the lumbar spine →VA disability calculator →

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Nexus Letter for Lumbar Spine: What It Must Say

The short answer

What a nexus letter is

What a Lumbar Spine nexus letter must contain

The diagnosis, by name and code

The theory of connection

The magic words, used correctly

A rationale, not a conclusion

A licensed clinician's signature and credentials

What a rater looks for in a Lumbar Spine nexus letter

A named diagnosis with imaging

The in-service event or loading

An answer to "it's just age"

Continuity after discharge

Nerve involvement noted