Appendix A

The Caluza Triangle is the foundational legal framework used by the Department of Veterans Affairs (VA) to establish direct service connection for a disability claim

Derived from the landmark Court of Appeals for Veterans Claims (CAVC) case Caluza v. Brown (1995), this three-part test serves as the ultimate checklist for claims evaluation. To secure service connection and receive disability compensation, a claim must satisfy all three prongs simultaneously. If even one corner of the triangle is missing, the VA will issue a denial.

The Three Elements of the Caluza Triangle

The framework functions as a chain of evidence, requiring a clear beginning, middle, and end.

1. Element One: A Current Medical Diagnosis

The VA cannot grant service connection for a condition that does not officially exist. There must be competent medical evidence documenting a current disability.

• What satisfies this: A formal diagnosis from a qualified medical professional recorded in service treatment records, VA medical center files, or private health records.

• The Nuance (Saunders v. Wilkie exception): Under newer case law, a definitive diagnosis is not always strictly required if chronic, un-diagnosed pain causing functional impairment can be clearly demonstrated. However, a formal medical diagnosis remains the cleanest, most secure way to satisfy this first prong.

2. Element Two: An In-Service Event, Injury, or Illness

There must be documentation showing that a specific incident, injury, chronic exposure, or disease occurred or was aggravated while on active duty.

• What satisfies this: Service medical records showing an emergency room visit, a line-of-duty investigation, or entries in an official personal log. For combat veterans, under 38 U.S.C. § 1154(b), the evidentiary standard is relaxed, allowing lay statements or "buddy letters" to prove an event occurred if it is consistent with the circumstances of their combat service.

• Presumptive Exceptions: For conditions covered under specific statutory presumptions (such as exposure to Agent Orange, Gulf War exposures, or the PACT Act toxic exposures), the in-service event or exposure is legally presumed if the veteran served in an eligible location during the designated timeframe.

3. Element Three: The Nexus (The Link)

The "Nexus" is the bridge connecting Element One (current diagnosis) to Element Two (in-service event). Statistically, this is where the vast majority of VA disability claims fail. The VA requires competent medical evidence establishing that the current disability is at least as likely as not caused or aggravated by the active-duty service event.

• What satisfies this: This link is typically established through a formal Nexus Letter or a medical opinion provided during a Compensation and Pension (C&P) Exam.

• The Legal Standard of Proof: The medical professional providing the opinion must use specific legal phrasing based on the "at least as likely as not" standard:

• "Is due to" or "More likely than not" (Near certainty)

• "Is highly likely" (Greater than 50% probability)

• "Is at least as likely as not" (50% or greater probability) – This is the minimum required to win a claim.

• "Less likely than not" (Less than 50% Probability) - Denied

Application: Direct vs. Secondary Service Connection

While the Caluza Triangle was established under the rules of direct service connection, its structure still applies when building a strategy for secondary conditions (disabilities caused or aggravated by an already service-connected issue):

• Direct Claim: Link an active-duty event directly to a current diagnosis (e.g., jumping out of planes in service leads directly to a current knee arthritis diagnosis).

• Secondary Claim: The "in-service event" prong shifts. Instead of linking back to active duty, the Nexus link connects the new secondary diagnosis to an existing, already rated service-connected disability (e.g., linking severe migraines secondary to service-connected tinnitus).

Understanding the three distinct corners of this framework allows a claim to be constructed like a tactical operation—ensuring every legal vulnerability is covered with hard evidence before submitting documentation to an adjudicator.

When the Department of Veterans Affairs (VA) calculates your combined disability rating, they don't just add the percentages together using standard math. If they did, a veteran with a 70% rating for PTSD and a 50% rating for a back injury would end up with a 120% rating, which isn't possible.

Instead, the VA uses a system colloquially known as "VA Math." This system is based on the concept of your body as a whole, undamaged entity worth 100%. Each separate disability takes a percentage out of what is left of your healthy body, not the original 100%.

Here is exactly how it works, how the calculations are run, and the rules that dictate your final number.

The Core Concept: Efficiency of a "Whole Person"

Think of your health as a pie chart representing 100% efficiency.

• When you are awarded a disability rating, that percentage chips away at the current size of the pie.

• The next disability rating chips away only at the remaining piece of the pie, not the whole thing.

Because of this, the higher your combined rating gets, the harder it is to climb closer to 100%. You experience a law of diminishing returns.

Step-by-Step Calculation Example

Let's look at a concrete example. Imagine a veteran has three separate service-connected disabilities, sorted from highest to lowest (which is exactly how the VA calculates them):

• Disability A: 50%

• Disability B: 30%

• Disability C: 10%

Here is how the VA math breaks down the sequence:

Step 1: Apply the Highest Rating

• Starting Health: 100%

• Disability A (50%): 100% x 0.50 = 50% disability.

• Remaining Efficiency: 100% - 50% = 50%.

• Current Combined Running Total: 50%

Step 2: Apply the Next Highest Rating to the Remainder

• Current Remaining Health: 50%

• Disability B (30%): You take 30% of the remaining 50% health, not the original 100%.
  50% x 0.30 = 15% additional disability

• Remaining Efficiency: 50% - 15% = 35%.

• Current Combined Running Total: 50% + 15% = 65%

Step 3: Apply the Final Rating to the New Remainder

• Current Remaining Health: 35%

• Disability C (10%): You take 10% of the remaining 35% health.
  35% x 0.10 = 3.5% additional disability

• Remaining Efficiency: 35% - 3.5% = 31.5%.

• Current Combined Running Total: 65% + 3.5% = 68.5%

The Final Step: Rounding to the Nearest 10%

The VA does not pay out at precise decimals like 68.5%. Once all disabilities have been sequentially factored in, the final running total is rounded to the nearest 10% alignment.

• If the total ends in 5% or higher, it rounds up to the next 10%.

• If the total ends in 4% or lower, it rounds down to the previous 10%.

In our example above, the raw score is 68.5%. Because the ending digit is 5 or higher, the VA rounds this up to a final combined rating of 70%.

Crucial Factors to Keep in Mind

1. Order of Operations Matters

The VA always arranges ratings from highest percentage to lowest percentage before starting the calculation. Calculating them out of order would change the math, so the sequence is strictly enforced.

2. The Bilateral Factor (The "Wildcard")

If you have disabilities affecting both sides of your body (e.g., left knee and right knee, or left shoulder and right arm), a special rule applies called the Bilateral Factor.

• The VA combines the bilateral disabilities first using regular VA math.

• They then calculate 10% of that combined value and add it as a bonus to that specific sub-total.

• This boosted figure is then thrown into the master calculation with your remaining non-bilateral conditions. This provides a slight mathematical edge to push a borderline rating to the next 10% bracket.

3. The Climb Gets Steeper

Because you are always multiplying by a fraction of a remaining percentage, reaching a true 100% combined rating without a single 100% individual rating requires an immense amount of combined lower conditions. For instance, if a veteran sits at a raw score of 94%, they need another separate 20% condition just to bump their raw score to 95.2%, which finally rounds up to 100%.

When you file a claim for VA disability compensation, medical records and service logs are crucial. However, they only tell part of the story. To truly understand how an injury impacts your life, the VA needs to hear from you.

That is where a VA Personal Statement comes in. Here is a detailed breakdown of what a personal statement is, the official forms you must use, what information to include, and a real-world example of what a winning statement looks like.

What is a VA Personal Statement?

Officially called a Statement in Support of a Claim, a personal statement is a written declaration that bridges the gap between your clinical medical codes and the daily reality of living with your condition.

The VA looks for three specific elements—often called the "Caluza Triangle"—to grant a service connection. Your personal statement is your best tool to support them:

1. The In-Service Event: You can describe exactly when and how the injury or illness occurred.

2. The Current Diagnosis: You can describe your current symptoms in your own words.

3. The Medical Nexus (Link): You can describe how the condition has persistently affected you from your discharge date until today.

The Official Forms You Need

While you can technically write a statement on a blank sheet of paper, the VA strongly prefers that you use their official forms. Using the correct form ensures your statement is legally binding and processed correctly.

• VA Form 21-4138 (Statement in Support of a Claim): This is the standard, multi-purpose form used when you (the veteran) are writing a statement about your own conditions. (Download the form here)

What Information is Required?

To make your personal statement effective, it needs to be structured, factual, and chronological. VA raters read dozens of these a day, so keeping it clear and concise is key. Ensure your statement includes the following four sections:

1. Administrative Details

Always include your identifying information at the top of the form or any attached pages:

• Full name and Date of Birth

• VA File Number or Social Security Number

• The specific condition the statement is referencing (e.g., "Statement in Support of my claim for Post-Traumatic Stress Disorder").

2. The In-Service Incident (The "What and When")

Describe the origin of the condition during your military service. Be as specific as possible with approximate dates, times, and locations. Explain what happened (e.g., a training accident, a combat deployment, or toxin exposure) and note whether you sought immediate medical attention.

3. Progression of the Condition (The "Nexus")

Explain what happened between your discharge and today. Tell the VA how the pain or symptoms persisted over the years, and mention if you self-treated with over-the-counter medications, braces, or lifestyle adjustments.

4. Current Symptoms & Severity (The "Daily Impact")

This is the most critical section. The VA rates disabilities based on how much they impair your life and ability to work.

• Frequency: How often do flare-ups occur? (e.g., daily, 3 times a week).

• Severity: Describe your worst days, not your average days. Use a 1–10 pain scale and descriptive language.

• Occupational Impact: How does this affect your job? (e.g., "I cannot stand for more than 15 minutes, causing me to miss 2–3 days of work per month").

• Social Impact: How does it affect your personal life? (e.g., "I can no longer sleep through the night or play with my children").

Example of a VA Personal Statement

Below is a realistic example of a completed VA Form 21-4138. This example demonstrates how to successfully argue for a secondary condition (a new injury caused by an existing service-connected injury).

VA Form 21-4138: Statement in Support of a Claim

Veteran’s Name: John E. Doe

VA File / SSN: XXX-XX-6789

Date of Birth: October 12, 1985

Condition: Left Knee Strain (Secondary to Right Knee Strain)

SECTION II: REMARKS

I am writing this statement to support my claim for a Left Knee Strain, secondary to my service-connected Right Knee Strain (currently rated at 10%). Because of the severe, chronic injury to my right knee, my gait has been permanently altered, forcing me to overcompensate and place the majority of my weight on my left leg. This has caused a severe, chronic secondary injury to my left knee.

1. Timeline and Progression of the Secondary Condition

• In-Service Context: I sustained a severe ligament tear in my right knee during an airborne training exercise in 2008, which was service-connected upon my discharge in 2012.

• Progression: Over the last four years, the pain in my right knee has worsened, causing it to frequently buckle. To avoid falling, I instinctively shift my weight to my left leg.

• Medical Nexus: In January 2025, I began experiencing sharp, localized pain, swelling, and a "grinding" sensation in my left knee. My private orthopedic doctor confirmed that this left knee strain is a direct result of "altered biomechanics and chronic overcompensation" due to my service-connected right knee injury (see attached medical report from Dr. Smith).

2. Current Symptoms and Severity

• Frequency: I experience dull, aching pain in my left knee daily, which escalates to a sharp, stabbing pain (8/10 on the pain scale) at least 3 to 4 times a week.

• Flare-ups: My left knee swells to twice its normal size if I am on my feet for more than 20 minutes. During a flare-up, which lasts 2–3 days, I experience a severe loss of range of motion and cannot fully straighten or bend my leg.

• Instability: The left knee now catches and "pops" when climbing stairs, causing sudden, unpredictable instability.

3. Impact on Occupational and Daily Life

• Occupational Impact: I work as an inventory manager, which requires walking the warehouse floor. Due to the severe pain and swelling in my left knee from overcompensating, I can no longer walk the floor for more than 15 minutes without needing to sit down and elevate my leg. I have used 8 days of sick leave in the past six months solely due to left knee flare-ups.

• Daily Living Impact: I can no longer perform basic household chores like mowing the lawn or standing to wash dishes without severe pain. My sleep is disrupted 3–4 nights a week because throbbing pain in my left knee wakes me up whenever I shift positions in bed.

Conclusion My left knee condition is a direct, debilitating result of compensating for my service-connected right knee injury. It severely impacts my daily mobility, sleep, and employment. I respectfully request that my Left Knee Strain be granted service connection as a secondary condition.

Quick Tips for Success

• One Condition Per Form: If you are claiming multiple conditions (e.g., Tinnitus and a Back Injury), write a separate VA Form 21-4138 for each one. Mixing them together can confuse the rater.

• Be Truthful, Not Modest: Veterans are notoriously conditioned to "suck it up" and downplay their pain. A personal statement is not the place to be modest. Be brutally honest about your absolute worst days.

• Keep it to 1–2 Pages: Raters have limited time. Be concise, use bullet points for symptoms, and stick to the facts. If you need more space than the form provides, attach a typed page with your name and SSN at the top.

When you are building a claim for VA disability compensation, your own words and medical records are vital. But sometimes, the VA needs outside perspective to truly understand the severity of your condition or to confirm an event that happened years ago.

This is where a Buddy Letter comes in. Here is a complete guide to what a buddy letter is, the official form required, what needs to go in it, and a real-world example to share with your writers.

What is a VA Buddy Letter?

Officially called a Lay Witness Statement, a buddy letter is a written statement provided by someone who knows you and can corroborate your claim.

Buddy letters are incredibly powerful because they provide "lay evidence"—firsthand, eyewitness accounts of your symptoms or the in-service event that caused them. They are typically written by:

• Military Buddies: To confirm an in-service injury, combat incident, or training accident (especially if military medical logs were lost or never created).

• Spouses or Family Members: To describe how your condition affects your daily life, mood, relationships, and behavior at home.

• Co-workers or Supervisors: To document how your service-connected disabilities impact your job performance or cause you to miss work.

The Official Form: VA Form 21-10210

In the past, the VA allowed buddy letters to be written on general forms or plain paper. Today, the VA strongly prefers—and often requires—that all lay witness statements be submitted on VA Form 21-10210 (Lay Witness Statement). (Download the form here)

What Information is Required in a Buddy Letter?

A great buddy letter doesn't need to be long, but it does need to be specific. A VA rater looks for four key elements when reading a Lay Witness Statement:

1. Identification & Relationship

The writer must identify themselves, state their relationship to the veteran, and explain how long (and how frequently) they have known the veteran.

• Example: "I am the veteran's spouse, and we have been married since 2014, living together daily."

2. Firsthand Knowledge (The "Eyewitness" Factor)

The writer should only describe things they have personally seen, heard, or witnessed. They should not guess at medical diagnoses.

• Good: "I see John struggle to get out of bed every morning due to severe back stiffness."

• Bad: "John has severe degenerative disc disease in his L5-S1 vertebrae." (Leave the medical terms to the doctors).

3. Current Symptoms & Real-World Impact

The writer should describe how the veteran's condition looks on a daily basis and during "flare-ups." They should answer:

• What does the veteran look like on their worst days?

• How has the condition changed the veteran's personality, hobbies, or abilities?

• How does it impact their employment or social life?

4. Clear, Chronological Details

If a military buddy is writing the letter to confirm an event, they need to provide approximate dates, locations, and a clear description of the incident (e.g., "During our deployment to Iraq in March 2010...").

Example of a VA Buddy Letter (VA Form 21-10210)

Below is a realistic example of a completed VA Form 21-10210 written by a veteran’s spouse to support a claim for Post-Traumatic Stress Disorder (PTSD) and chronic insomnia.

VA Form 21-10210: Lay Witness Statement

Veteran’s Name: Robert M. Vance

Veteran’s VA File / SSN: XXX-XX-4321

Witness Name: Sarah J. Vance

Witness Relationship to Veteran: Spouse

Witness Contact Info: (555) 019-2834 | sarah.vance@email.com

SECTION III: STATEMENT

I am writing this statement on behalf of my husband, Robert M. Vance, regarding his claim for Post-Traumatic Stress Disorder (PTSD) and Insomnia. We have been married for twelve years, and I see the profound, daily impact these conditions have on his life.

1. Observations of Sleep Disturbances and Nightmares Robert rarely sleeps more than 3 to 4 hours a night. Nearly every night, he tosses and turns for hours before falling asleep. At least 3 times a week, he wakes up screaming, drenched in sweat, and completely disoriented from severe combat nightmares. When this happens, his heart races, and it takes him hours to calm down. Because of this chronic insomnia, he is perpetually exhausted, which severely limits his patience and energy during the day.

2. Social Isolation and Hypervigilance Over the last five years, Robert’s anxiety has worsened significantly. He completely avoids crowded places. When we go to a grocery store or restaurant, he exhibits extreme hypervigilance—he insists on sitting facing the door, constantly scans the room, and grips his hands tightly if someone walks up behind him. If a restaurant is too loud, we have to leave immediately. As a result, we no longer host family gatherings, go to the movies, or attend our children's school functions. He has isolated himself from his lifelong friends.

3. Occupational and Emotional Impact Robert’s irritability and panic attacks have made it incredibly difficult for him to maintain a normal routine. He experiences sudden bouts of intense anger over minor frustrations. Last month, a loud noise at his workplace triggered a severe panic attack, causing him to lock himself in his office for two hours to stop shaking. He has missed 5 days of work in the past two months because he was too emotionally drained or sleep-deprived to drive safely.

Conclusion The man Robert is today is vastly different from the man I married before his deployments. His PTSD and sleep issues dictate every aspect of our family’s daily life. Thank you for your time and consideration of his claim.

Quick Tips for Your Buddy Letter Writers

• Stick to the Facts: Don't try to sound like a doctor or a lawyer. The VA wants to hear honest, human observations.

• Focus on the "Before and After": If the writer knew the veteran before military service, it is incredibly effective for them to describe how much the veteran changed after coming home.

• Keep it Legible: It is best to type the statement into the fillable PDF form and print it out for a wet signature. If it must be handwritten, ensure it is written neatly in black or blue ink.

If a personal statement is your voice, and a buddy letter is your family's voice, a Nexus Letter is the medical professional’s voice.

Of all the evidence you can submit with a VA disability claim, a well-crafted nexus letter is often the single most critical piece of evidence for securing service connection—especially for complex or secondary claims. Here is a complete guide to what a nexus letter is, how it is submitted, and what it needs to look like to succeed.

What is a VA Nexus Letter?

A nexus letter is an official medical opinion written by a licensed healthcare provider (such as a doctor, physician assistant, nurse practitioner, or psychologist). Its sole purpose is to establish a nexus—a medical link—between your current diagnosed disability and your military service.

The VA will not grant service connection unless there is clear evidence that your service caused or aggravated your condition. A nexus letter provides the clinical rationale that proves this link exists.

The Form Used to Send It

Unlike personal statements or buddy letters, there is no official VA form for a nexus letter. Instead, it is written directly on the medical provider’s official business letterhead and submitted as an attachment to your claim (VA Form 21-526EZ).

💡 Website Tip: Sometimes, a provider will write their nexus opinion directly into a DBQ (Disability Benefits Questionnaire), which is an official VA form. However, a standalone, formal letter on business letterhead remains the gold standard for complex claims.

The 5 Required Elements of a Winning Nexus Letter

The VA has strict legal standards for what makes a medical opinion valid. If a doctor simply writes, "I think John's back pain is from the Army," the VA will reject it. To be legally sufficient, a nexus letter must contain the following five elements:

1. The Doctor’s Credentials

The letter must establish that the author is an expert qualified to give an opinion on your specific condition.

• Example: A nexus letter for PTSD should come from a licensed psychologist or psychiatrist; a letter for a knee injury should come from an orthopedist or physical therapist.

2. Evidence of a Full Record Review

The provider must explicitly state that they reviewed your entire medical history, including your military service medical records (STRs) and post-service treatment logs. The VA needs to know this opinion isn't based on guesswork.

3. A Clear Diagnosis

The letter must confirm that you currently have a formal, clinical diagnosis of the condition you are claiming.

4. The "VA Standard of Proof" (The Legal Language)

The VA does not require 100% scientific certainty. Instead, they use specific legal phrases to measure probability. The doctor must use one of these exact phrases:

• "Is at least as likely as not" (50% or greater probability) – This is the minimum required to win a claim.

• "Is highly likely" (Greater than 50% probability)

• "Is due to" or "More likely than not" (Near certainty)

5. Medical Rationale (The "Why")

This is the most important part. The doctor must provide a clinical explanation linking your service to your diagnosis. They should cite medical literature, peer-reviewed studies, or anatomical facts to explain how the service event caused the current condition.

Example of a VA Nexus Letter

Below is a realistic template of a nexus letter written by a private doctor, linking a veteran’s Sleep Apnea to their service-connected PTSD (a common secondary claim).

[Doctor / Clinic Letterhead]

Apex Medical Group 123 Health Science Way, Suite 400

Phone: (555) 012-3456

Date: May 20, 2026

RE: Medical Nexus Opinion for Veteran Robert M. Vance

Veteran’s DOB: October 12, 1985

Veteran’s SSN: XXX-XX-4321

To Whom It May Concern,

I am Dr. Jane Smith, MD, a board-certified pulmonologist and sleep medicine specialist with over 15 years of clinical experience. I am writing this independent medical opinion to address the relationship between Mr. Robert M. Vance’s diagnosed Obstructive Sleep Apnea (OSA) and his service-connected Post-Traumatic Stress Disorder (PTSD), currently rated at 70%.

Review of Medical Records: To formulate this medical opinion, I have personally reviewed Mr. Vance’s complete Department of Veterans Affairs medical records, private treatment logs, service treatment records (STRs), and his overnight polysomnography (sleep study) report dated January 14, 2025.

Medical Narrative & Rationale: Mr. Vance was formally diagnosed with severe Obstructive Sleep Apnea following his 2025 sleep study, which indicated an Apnea-Hypopnea Index (AHI) of 32, requiring the use of a CPAP machine. Mr. Vance has been service-connected for PTSD since 2014.

There is a well-established medical consensus linking severe PTSD to the development and worsening of Obstructive Sleep Apnea. Mr. Vance suffers from chronic hyperarousal, severe nocturnal panic attacks, and sleep fragmentation directly related to his PTSD. To manage these symptoms, he is prescribed a high dosage of selective serotonin reuptake inhibitors (SSRIs) and Trazodone.

Clinical literature demonstrates that chronic PTSD-induced hyperarousal alters upper airway stability during sleep. Furthermore, the medications prescribed to manage his PTSD contribute to upper airway muscle relaxation, significantly increasing pharyngeal collapsibility during sleep. (See Spiegel et al., Journal of Clinical Sleep Medicine, "The Reciprocal Relationship Between PTSD and OSA").

Expert Medical Conclusion: Based on my physical examination of the veteran, a thorough review of his medical history, and an evaluation of the peer-reviewed medical literature, it is my professional medical opinion that it is at least as likely as not (50% or greater probability) that Mr. Vance’s Obstructive Sleep Apnea was proximately caused by, and is chronically aggravated by, his service-connected Post-Traumatic Stress Disorder.

Respectfully submitted,

[Handwritten Signature]

Jane Smith, MD Board Certified in Pulmonology and Sleep Medicine

License No: #98765432-MD

Quick Tips for Veterans Seeking a Nexus Letter

• Provide the Records First: Do not ask a doctor for a nexus letter without giving them your military Service Treatment Records (STRs) first. They cannot legally state they reviewed them if they haven't seen them.

• Educate Your Private Doctor: Many private doctors want to help but do not understand VA terminology. Print out the required "VA Standard of Proof" phrases (like "at least as likely as not") and show them to your doctor so they use the exact legal language the VA requires.