Direct, secondary, and aggravation: which claim are you making?

Before a physician can write anything useful, there is a question you have to answer: what kind of connection are you claiming? The three routes require different evidence and different medical reasoning, and choosing the wrong one is a common reason otherwise strong claims fail.

Direct service connection

The condition began during service, or was caused by something that happened during service. This is the most straightforward route conceptually and often the hardest to document, because it depends on what is in your service treatment records.

What a medical opinion contributes here is usually one of two things. Either it explains why a condition diagnosed after discharge is nonetheless attributable to an in-service injury or exposure — the natural history of the disease, the latency period, the mechanism. Or it addresses the absence of continuous treatment, which adjudicators sometimes read as evidence the condition resolved. Many service members managed injuries without reporting them, and degenerative conditions progress silently. A physician can say that plainly.

Secondary service connection

An already service-connected condition caused a new one. This is where a large share of successful claims now sit, and it is the route most dependent on a proper medical opinion, because the entire claim rests on a causal mechanism that only a clinician can explain.

The requirements are specific: you need an established service-connected primary condition, a current diagnosis of the secondary condition, and medical evidence that the first caused or aggravated the second. That third element is the nexus opinion, and a vague assertion will not carry it. What carries it is a described mechanism.

Secondary claims also cover aggravation of a non-service-connected condition by a service-connected one. If you had a condition before or outside service and a service-connected condition made it permanently worse, that increment is compensable even though the underlying condition is not.

Aggravation of a pre-existing condition

You entered service with a condition, and service made it permanently worse. This is medically the most demanding of the three, because it requires establishing two things rather than one: a baseline before service, and a worsening beyond what the condition's natural progression would have produced on its own.

That second point is where these claims are usually lost. Nearly every chronic condition gets worse over twenty years. The question is whether service made it worse faster or further than it otherwise would have. Answering that requires a physician to compare your entrance examination against your separation examination and your current status, and to state what the expected trajectory would have been without the service exposure.

How to tell which applies

1. 01Do you already have a service-connected condition that you believe led to this one? If yes, you are likely making a secondary claim.
2. 02Was the condition noted on your entrance examination? If yes, aggravation. If no, the presumption of soundness generally applies and you are making a direct claim.
3. 03Did the condition begin during service, or result from something that happened during service? If yes, direct.

It is possible for more than one route to apply, and a well-written opinion can address alternatives — arguing primarily for direct connection while noting that the evidence would also support secondary connection to an already-rated condition. That gives the adjudicator two paths to the same result.