The VA Bilateral Factor Explained: What 38 CFR § 4.26 Means for Your Health Records
If you’re tracking medical records for a condition that affects both knees, both hips, or both shoulders, you may have run into the term bilateral factor. It sounds technical, but the idea behind it is simple: dealing with a problem on both sides of your body is often harder than dealing with the same problem on just one side.
This guide walks through what the bilateral factor means, how it’s calculated, and why clear medical documentation matters.
What Does “Bilateral” Mean in a Medical Record?
In medical language, bilateral just means “both sides.” A bilateral condition is one where a matching, paired body part has a service-connected issue on both the left and the right.
That’s different from having two unrelated conditions. A left elbow injury and a right hip problem aren’t bilateral, they’re just two separate issues. But ongoing problems in both your left knee and your right knee? That’s a bilateral condition.
Under 38 CFR § 4.26, the bilateral factor can apply to matching body parts, including:
- Both arms or both legs
- Both knees, ankles, or hips
- Both shoulders, elbows, or wrists
- Matching paired muscle groups, like both hamstrings
What it does not cover: Eyes, ears, and internal organs (like lungs or kidneys) are rated under their own separate rules and are not part of this calculation. Conditions like flat feet that affect both feet are also usually rated as one single condition with its own code, rather than being run through the bilateral math.
Why Does This Rule Exist?
Think about how the body protects against an injury. If you hurt your left knee, you can lean on your right leg for balance and stability. That “good side” acts like a backup.
But when both knees are hurt, that backup disappears. There is no stronger side left to absorb the extra strain.
The rule reflects that reality. When a disability affects both sides of a paired body part, VA math treats that combined impact as slightly greater than if you just added the two individual numbers together. It is a recognition that losing a “good side” makes daily movement noticeably harder.
How VA Disability Math Works (Before Bilateral Factor)
VA doesn’t simply add percentages together. Instead, it uses a combined ratings table based on how much “efficiency” you have left. For example, a 20% rating combined with a 10% rating comes out to 28%, not 30%, under the VA’s standard method.
Once you understand this baseline, the bilateral factor is easier to follow. It’s an extra step added on top of that same table.
Step-by-Step: How the Bilateral Factor Is Calculated
- Step 1. Combine the paired ratings: Find the ratings for the matching left and right conditions. Combine them using the VA’s standard combined ratings table.
- Step 2. Calculate 10% of that number: Take 10% of the combined bilateral subtotal from Step 1.
- Step 3. Add the bonus directly: Add that 10% figure straight onto the total using simple addition, not the combined ratings table. This creates your adjusted bilateral value.
- Step 4. Combine with other conditions and round: Combine that new number with any other, unrelated service-connected conditions using the standard table. Round the final total to the nearest 10%.
A Simple Example
Say a veteran has a service-connected right knee condition rated at 20% and a left knee condition rated at 10%.
| Step | What Happens | Result |
| 1. Combine both ratings | 20% + 10% (VA table) | 28% |
| 2. Find 10% of that value | 10% of 28% | 2.8% |
| 3. Add directly | 28% + 2.8% | 30.8% |
| 4. Round to nearest 10% | VA rounding rule | 30% |
According to the federal regulation, this bilateral adjustment is added directly, not combined through the table. That is why it can push your final number higher.
Does the Bilateral Factor Always Apply?
Does a 0% rating count toward the bilateral factor?
No. Both sides generally need a rating of 10% or higher for the bilateral math to come into play. A 0% rating documents that a condition is service-connected, but it does not add any value to this specific calculation.
Can secondary conditions qualify?
Yes. The regulation treats primary conditions and secondary conditions the same way. If a right hip condition is primary and a left hip condition became service-connected later as a secondary issue, both can be treated as a bilateral pair.
The Domino Effect: How One Injury Can Lead to Another
Here is a way to picture how secondary conditions often develop. Imagine a row of dominoes. The first domino falls (that is your original service-connected injury) say a left knee condition. As you naturally shift your weight and change how you walk to protect that knee, the next domino starts to tip.
You put increased strain on your right knee. Over time, that strain may cause a new issue, like right knee joint pain (osteoarthritis).
This is known as a compensation pattern. It shows why it is important to have clear medical records organized by timeline. If your records show how one joint problem impacts another, this connection helps provide a full view of your health.
Clear documentation makes this pattern easy to see.
Why Clear Documentation for Both Sides Matters
The bilateral factor calculation depends on clear medical evidence. It cannot be assumed from a general note. Records that clearly support a bilateral picture tend to include:
- Side-specific findings: Separate range-of-motion measurements for the left and right joint, rather than a vague note about “bilateral pain.”
- Parallel tracking over time: Proof that both sides have been checked and monitored consistently.
- Individual functional descriptions: Notes on how each side affects daily activities, since one side is often worse than the other.
Trajector Medical offers medical evidence reviews to help veterans organize this kind of documentation. This support is focused on helping records be well-organized and easy to follow. It does not involve filing paperwork, offering legal advice, or making eligibility determinations.
Veterans remain fully in control of how they use their organized records and may choose to work with an accredited VSO, claims agent, or attorney for the official next steps in their benefits journey.
