Secondary Aggravation Claims

Most secondary claims are argued as causation: my service-connected condition caused this new one. When VA finds the second condition already existed, the claim usually ends there. It should not. 38 CFR §3.310(b) provides service connection for the worsening of a condition that is not service connected, where a service-connected disability caused that worsening. It is a separate theory, with a separate evidentiary requirement, and it is regularly left on the table.

Two different rules, both called aggravation

Before anything else, this distinction. Veterans conflate these constantly, and the conflation costs claims, because the evidence each rule wants is not the same evidence.

A worked contrast. A veteran enlisted with a documented knee injury from high school, which got markedly worse during four years of infantry service: that is a §3.306 question. A veteran developed osteoarthritis in the left knee in their fifties, unrelated to service, and their service-connected right ankle fusion has forced years of altered gait onto that left knee: that is a §3.310(b) question. Same joint, same word, entirely different claim.

What §3.310(b) requires

The regulation does three things:

1. It service connects any increase in severity of a non-service-connected disease or injury that is proximately due to a service-connected disability, and not due to the natural progress of the non-service-connected condition;
2. It says VA will not concede aggravation unless the baseline level of severity of that condition is established by medical evidence; and
3. It directs the rating activity to determine baseline and current levels of severity under the rating schedule, and to work out the extent of aggravation by deducting the baseline — and any natural-progress worsening — from the current level.

The aggravation theory was recognised in case law before it was written into the regulation, in Allen v. Brown, 7 Vet. App. 439 (1995). The 2006 amendment to §3.310 added the baseline requirement, which is the part that now decides most of these claims.

How the arithmetic works

Understanding the mechanics is what makes an aggravation claim winnable, because it tells you what the medical opinion has to produce.

• Current level of severity, expressed as a percentage under the applicable diagnostic code;
• less the baseline level, expressed the same way;
• less any increase attributable to natural progress of the condition;
• equals the compensable increment. That increment is what is service connected.

The baseline is where these claims fail

Almost every denied §3.310(b) claim we look at fails at the same place. Either no baseline was ever established, or the examiner declined to identify one, or the decision asserts that a baseline cannot be determined and treats that as the end of the matter.

Two points are worth knowing about how the requirement is actually written.

First, the baseline does not have to predate the aggravation. The regulation accepts medical evidence created before the onset of aggravation or the earliest medical evidence created at any point between the onset of aggravation and the evidence establishing the current level of severity. If there are no records from before your service-connected condition started doing damage, the earliest records you do have can serve. Veterans give up on these claims believing they need records they never had. Often they do not.

Second, the baseline is a medical and rating question, not a memory test. It is established by evidence in the record and expressed in terms of the rating schedule. This is precisely the kind of determination a C&P examiner is asked to inform, which is why an examination that fails to address it is incomplete rather than merely unhelpful.

The May 2026 exam-necessity update

Effective 1 May 2026, VA revised M21-1 IV.i.1.B, the guidance on when a VA examination or medical opinion is necessary, with changes directed at aggravation claims specifically. It was issued alongside the revisions that folded the Federal Circuit's decision in Spicer v. McDonough into the manual's causation sections — see our page on Spicer and the but-for standard, which also deals with the false rumour that secondary claims were abolished.

Two practical consequences. Exam-necessity guidance governs whether the duty to assist requires VA to obtain an opinion in the first place — so if VA decided your aggravation claim without an examination, that decision is worth testing against the current version of IV.i.1.B rather than the version in force when you filed. And because the M21-1 is guidance rather than regulation, and the Board is not bound by it under 38 CFR §19.5, the manual is a useful argument at a regional office and not the last word on appeal. The manual text is published on VA's KnowVA knowledge base.

How to evidence an aggravation claim

1. Establish the baseline yourself

Do not leave it to the examiner to go looking. Identify the earliest medical evidence describing the non-service-connected condition and put it in front of them. Useful sources:

• The first diagnosis of the condition, wherever it was made;
• Imaging with dates — X-rays, MRI, and their radiology reports, which are the most objective baseline evidence available for orthopaedic claims;
• Pulmonary function tests, sleep studies, endoscopy reports, laboratory panels — any objective measure that has been repeated over time;
• Treatment frequency and medication dose history, which document severity even where no formal measurement exists;
• Occupational and functional records showing what you could do then compared with now.

2. Document the trajectory

Aggravation is a claim about change over time. It is proved with a sequence, not a snapshot. Build a chronology: baseline evidence, the onset or worsening of the service-connected condition, and the measurable deterioration that followed. Where you have repeated objective measures, put them side by side. Two imaging reports five years apart with the service-connected condition in between are worth more than any amount of narrative.

3. Get an opinion that answers the right questions

A usable aggravation opinion answers four things, each with reasoning tied to your records:

1. Is it at least as likely as not that the service-connected condition aggravated the claimed condition beyond its natural progression?
2. What was the baseline level of severity before the aggravation began, and which specific evidence establishes it?
3. What is the current level of severity, and by what measure?
4. How much of the difference is attributable to natural progress, and how much to the service-connected condition?

Question two is the one to insist on. An opinion that concedes aggravation but identifies no baseline hands the adjudicator a reason to deny — and the second half of §3.310(b) as its justification. The nexus letter guide sets out the full structure, and a well-drafted DBQ can carry some of this where the diagnostic code has measurable criteria.

4. Say the word

Write "caused or aggravated by" in the claim itself. Not "caused by." Both prongs, in terms, every time. A claim that says only "caused by" invites an examination request that asks only about causation, and an examiner who answers only what was asked. That single omission accounts for a remarkable share of these denials.

Where aggravation is often the stronger theory

• Degenerative joint disease. Arthritis that would have progressed anyway, accelerated by altered gait or compensatory loading from a service-connected joint.
• Hypertension and cardiac conditions. Pre-existing and multifactorial, but plausibly worsened by a service-connected mental health condition or by significant weight gain — see obesity as an intermediate step.
• Sleep apnea. Diagnosed before the weight gain or before the service-connected condition, and measurably worse since. AHI figures from sequential sleep studies are unusually good baseline evidence.
• GERD. Long-standing reflux that changed character after years of NSAIDs for a service-connected musculoskeletal condition.
• Non-service-connected mental health conditions. Worsened by the burden of chronic service-connected pain or disability.

After a denial

• No baseline was established. Get an opinion that identifies one from the earliest available records and file a supplemental claim.
• The examiner addressed causation only. The aggravation prong was never adjudicated. That is an inadequate examination — see inadequate C&P exams — and can be raised through higher-level review or as a duty-to-assist error.
• No examination was provided at all. Test that against the current M21-1 IV.i.1.B exam-necessity guidance.
• The decision misapplied the baseline rule — for instance by requiring evidence predating the aggravation when the regulation also permits the earliest evidence created afterwards. That is an error on the record, and HLR is built for it.

Lane choice affects both timing and your effective date. Our comparison of HLR versus supplemental claims walks through the trade-off.

What we do

We find the baseline before we do anything else, because that is what the regulation turns on and it is almost always sitting in records nobody has read in sequence. Then we make sure the medical opinion states the baseline in terms the rating schedule can use, separates natural progress from the service-connected contribution, and answers both prongs rather than one. Where a decision has denied aggravation without ever establishing a baseline, we say exactly that, citing the part of §3.310(b) that required it.