When a veteran has service-connected disabilities affecting both arms or both legs, the VA doesn't simply add the ratings together. It applies a special calculation called the bilateral factor, which is designed to recognize that bilateral extremity disabilities create a combined functional impact greater than either disability alone. At higher combined ratings, the bilateral factor routinely adds $50 to $100 or more per month in compensation. Understanding this rule, and catching the cases where raters apply it incorrectly, can mean a meaningful, permanent difference in monthly pay.
Missed bilateral factor is one of the most common rater calculation errors. If both sides of a paired condition are rated but the bilateral factor was not applied, or was applied to the wrong group of disabilities, the combined rating is wrong and can be corrected through a supplemental claim or appeal.
The bilateral factor is established under 38 CFR 4.68. It applies when a veteran has service-connected disabilities of paired extremities: both arms, both legs, or one arm and one leg. The rule recognizes that losing full function in both hands, for example, is not simply twice the impairment of one hand. The combined effect on work capacity and daily function is multiplicatively worse.
The calculation works as follows:
A veteran with 20% bilateral knee ratings:
The bilateral factor is applied before combining the bilateral group with other disabilities. Veterans (and sometimes VA raters) often make the mistake of applying it at the wrong step.
The bilateral factor applies when:
The factor applies whether the bilateral conditions are identical (bilateral knee OA) or different (right knee instability and left knee meniscus tear). What matters is that both extremities are affected and rated.
The bilateral factor does not apply to:
Many veterans with bilateral joint conditions have only one side service-connected because they only filed one claim, or because one side wasn't documented in service records. Common bilateral conditions that warrant evaluating both sides:
If your claim currently only includes one side of a bilateral condition, it's worth evaluating whether the other side can be added.
Adding a bilateral claim for the second extremity is done through a new claim or a supplemental claim for the unrated side. The service connection argument for the second side often mirrors the first side's argument, with the additional point that bilateral presentation is consistent with the bilateral occupational exposure during service.
A nexus letter for bilateral claims should explicitly address both sides and explain why the occupational history produced bilateral rather than unilateral findings.
The VA doesn't add percentages directly. It uses a combined ratings table (also called the "whole person" method). Under this system:
The bilateral factor is applied as an add-on to the bilateral group's combined value before that group is fed into the overall combined rating calculation.
Small errors in how the bilateral factor is applied, or in which disabilities are included in the bilateral group, can produce an incorrect final combined rating. Veterans who suspect their combined rating was calculated incorrectly can request a detailed explanation of the rating calculation or work with a VSO or attorney to verify it.
For veterans with multiple joint conditions affecting paired extremities, Flat Rate Nexus provides physician-signed independent medical opinions at flatratenexus.com. The site includes a free combined rating calculator and a nexus letter grader to help ensure all conditions are properly documented and rated.
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