Subtalar / Midfoot Arthritis Secondary to Ankle Fusion (Arthrodesis)

Yes. Under 38 CFR § 3.310(a), any disability proximately caused or chronically worsened by a service-connected condition is itself service-connected. Subtalar / Midfoot Arthritis is a documented secondary pairing for Ankle Fusion (Arthrodesis) with strong medical evidence. A nexus letter from a qualified physician linking the two conditions is the most reliable way to establish this connection.

The gold standard is a private nexus opinion stating — to at least a 50% probability ("at least as likely as not") — that the secondary condition was caused or aggravated by the primary service-connected condition. Peer-reviewed medical literature supporting the physiological mechanism strengthens the nexus. Treatment records documenting the onset or worsening of the secondary condition in temporal relation to the primary are supporting evidence.

The VA rates Subtalar / Midfoot Arthritis separately under its own 38 CFR Part 4 diagnostic code, then combines it with Ankle Fusion (Arthrodesis) and all other service-connected ratings using the combined ratings formula under § 4.25. The formula applies the whole-person concept: a 50% combined existing rating plus a new 30% rating yields 65% (rounded to 70%), not 80%.

38 CFR § 3.310(a) states: "Disability which is proximately due to or the result of a service-connected disease or injury shall be service connected." The aggravation variant under § 3.310(b) applies where the primary condition permanently worsens a pre-existing disability beyond its natural progression. Both standards require a showing of nexus — a medical or scientific link between the primary condition and the secondary.

The medical evidence supporting Subtalar / Midfoot Arthritis as secondary to Ankle Fusion (Arthrodesis) is rated strong. Ankle (tibiotalar) arthrodesis eliminates dorsiflexion and plantarflexion at the tibiotalar joint, forcing compensatory hypermobility at the subtalar, talonavicular, and calcaneocuboid joints during gait. These adjacent joints are biomechanically designed for inversion/eversion and rotational accommodation — not sagittal-plane motion — and the forced redistribution of motion accelerates articular cartilage wear. Long-term follow-up studies demonstrate that 70-90% of ankle fusion patients develop radiographic subtalar arthritis within 10-15 years, with 25-30% becoming symptomatic and requiring additional surgical intervention. The midfoot (Chopart and Lisfranc joints) similarly develops compensatory degenerative changes, producing a progressive pattern of hindfoot and midfoot arthritis.

The VA will not solicit nexus evidence on your behalf for secondary claims. In practice, a written nexus opinion from a private physician or independent medical examiner is essential — the VA's Compensation & Pension (C&P) examiner is not required to produce a favorable nexus opinion, and the VA has discretion to weigh competing opinions. Submitting a private nexus letter at the time of filing is the most reliable strategy.