Posterior Tibial Tendon Dysfunction (PTTD) Secondary to Pes Planus (Flat Feet)

Yes. Under 38 CFR § 3.310(a), any disability proximately caused or chronically worsened by a service-connected condition is itself service-connected. Posterior Tibial Tendon Dysfunction (PTTD) is a documented secondary pairing for Pes Planus (Flat Feet) 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 Posterior Tibial Tendon Dysfunction (PTTD) separately under its own 38 CFR Part 4 diagnostic code, then combines it with Pes Planus (Flat Feet) 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 Posterior Tibial Tendon Dysfunction (PTTD) as secondary to Pes Planus (Flat Feet) is rated strong. The posterior tibial tendon is the primary dynamic arch support structure, and in pes planus it is chronically overloaded as it attempts to maintain medial longitudinal arch integrity against excessive pronation forces. Progressive posterior tibial tendon dysfunction (PTTD) is the natural biomechanical consequence of flatfoot deformity — the tendon undergoes repetitive microtrauma, collagen degeneration, and eventual elongation or rupture. PTTD follows a staged progression: Stage I (tendinitis without deformity), Stage II (flexible flatfoot worsening), Stage III (rigid flatfoot), Stage IV (valgus tilting of the talus). Military service accelerates this cascade through high-impact training, heavy load carriage, and prolonged standing. PTTD is the leading cause of adult-acquired flatfoot deformity.

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.