What service connection requires
The VA requires three things to grant service connection:
Pillar 1: Current medical diagnosis
You must have a current, documented diagnosis from a qualified medical professional. "My knee hurts" is not enough, you need "bilateral patellofemoral syndrome" or "degenerative joint disease of the right knee."
How to get it
- Visit your VA primary care provider
- See a private physician (the VA accepts private medical evidence)
- Request specific diagnostic tests: X-rays, MRIs, sleep studies, audiograms
- Ask your doctor to use the specific diagnostic terminology the VA recognizes
Pillar 2: In-service event, injury, or exposure
You must show something happened during military service that caused or contributed to your condition. This can be:
- A specific injury (fall, vehicle accident, blast exposure)
- Repeated exposure (noise, chemicals, physical strain)
- An in-service diagnosis or sick call visit
- Documented duties that caused wear and tear (rucking, lifting, standing)
How to document it
- Service Treatment Records (STRs) are the strongest evidence
- Line of duty reports, incident reports
- Deployment records, personnel records
- Buddy statements from people who witnessed the event or exposure
Pillar 3: Medical nexus
A nexus is the link between Pillar 1 and Pillar 2, medical evidence stating your current condition is connected to your military service.
Types of nexus evidence
- Nexus letter: A written opinion from a doctor (see our Nexus Letter guide)
- Favorable C&P exam opinion: The VA examiner states the connection
- Presumptive service connection: Certain conditions are automatically connected (see First Year guide)
- Continuity of symptoms: Medical records showing the same condition from service to present
Evidence hierarchy (strongest to weakest)
- Service Treatment Records showing in-service diagnosis
- Medical nexus letter with literature-supported rationale
- Favorable C&P exam opinion
- Private medical records showing continuous treatment
- VA medical records
- Buddy statements and lay evidence
- Personal statements
Secondary service connection
If you already have a service-connected condition, you can claim conditions caused or aggravated by it. Common secondary connections:
- PTSD → Sleep apnea, depression, substance abuse
- Back injury → Radiculopathy, hip/knee problems (altered gait)
- Hearing loss → Tinnitus (and vice versa)
- Diabetes → Peripheral neuropathy, erectile dysfunction, vision problems
- Knee injury → Opposite knee (compensating), back problems
For secondary claims, your nexus letter must explain how the primary condition caused or worsened the secondary condition.
Buddy statements (VA Form 21-10210)
A buddy statement is sworn testimony from someone who can support your claim. Strong buddy statements:
- Come from people who witnessed your condition or injury
- Include specific dates, locations, and details
- Describe observable symptoms, not medical diagnoses
- Explain how the condition affects your daily functioning
- Are written in the person's own words (not a template)
Who should write them
- Fellow service members who served with you
- Spouses, parents, or close family who've seen your condition progress
- Coworkers who've witnessed your limitations
- Friends who knew you before and after service