Veterans with a service-connected knee or back condition often develop foot pain years later and assume it is unrelated aging. Frequently it is not. When one joint stops working normally, the body redistributes load, and the feet absorb a large share of that redistribution. 38 CFR 3.310 recognizes this: a condition caused or aggravated by an already service-connected disability can itself be service connected.
What a secondary claim requires
Three things, and the third is where most claims are decided:
- A current diagnosed foot condition - plantar fasciitis, acquired flatfoot, metatarsalgia, or another documented disability
- An already service-connected disability capable of altering gait or load distribution - a knee, ankle, hip, or spine condition
- Competent medical evidence connecting the two, either by causation or by aggravation
The biomechanics an opinion has to explain
A persuasive opinion does not simply assert that a bad knee causes foot pain. It describes the mechanism in the specific veteran: which direction the gait shifted, which foot took the extra load, and why that pattern produces the diagnosed condition rather than some other one.
Common patterns include antalgic gait - shortening time on the painful limb, which loads the opposite foot - reduced ankle dorsiflexion increasing strain through the plantar fascia, and a spine condition changing pelvic alignment and therefore foot strike. Our knee instability guide and knee secondary to back and hip describe the upstream half of the same chain.
Where veterans start
Every case is different, and there is no obligation at any step. When veterans want to understand what their records actually support, these are the two most common starting points:
- Medical records review
A licensed physician reviews your records for a $250 flat fee and identifies which foot and ankle conditions the available evidence may support. The fee is refunded in full if nothing supportable is identified.
- Nexus letter
When the records support one, a licensed provider writes the medical opinion that addresses the link between your foot or ankle condition and your service or an already service-connected disability.
Aggravation is its own basis
38 CFR 3.310(b) compensates aggravation separately from causation. A veteran who already had mild flat feet, and whose condition worsened measurably after a service-connected knee changed how he walks, is describing aggravation - and the rating reflects the degree of worsening over the pre-aggravation baseline.
That distinction matters because aggravation is often the honest theory when causation is not supportable. An opinion that overstates causation where the record shows aggravation is weaker, not stronger.
Evidence that supports the theory
The strongest secondary foot claims show the sequence in the records themselves:
- Treatment notes documenting the service-connected condition and an antalgic or altered gait
- Physical therapy records describing compensation patterns, weakness, or asymmetry
- The first records showing foot complaints, dated after the primary condition worsened
- Orthotics or footwear modifications prescribed for the foot
- Lay statements describing how the veteran's walking changed and when
Where these claims go wrong
Two failures are common. The first is a timeline that does not fit - foot complaints predating the primary condition's worsening, which undercuts causation but may still support aggravation. The second is an opinion that never engages competing causes such as weight, age, diabetes, or a civilian job spent on concrete. A reviewer who addresses those factors directly writes a more credible opinion than one who ignores them.
That is also why reviewing the actual records comes first. Our medical records review identifies which theories the file supports before anyone writes anything, and our nexus letter service produces the opinion when the evidence supports one. For what a probative opinion contains, see our nexus letter guide.