The Kinetic Chain: How Lower Extremity Gait Compensation Damages Adjacent Joints Over Time (VA Secondary Claim Guide for Veterans)

By Dr. Drew Brennes, D.C. — The Nexus Letter Doctor

TL;DR — Quick Answer: A service-connected foot or ankle injury rarely stays "just" a foot or ankle injury. Over years of walking on a compromised base of support, the body develops compensatory movement patterns — altered gait — that transmit abnormal loads upward through the knees, hips, and low back. These compensatory loads cause measurable, durable damage to adjacent joints. The peer-reviewed orthopedic and biomechanical literature has thoroughly documented this cascade, and the VA's own secondary service connection framework (38 C.F.R. § 3.310) explicitly recognizes it. If you have a service-connected lower extremity condition and are now experiencing knee, hip, or back symptoms, you likely have a valid secondary claim. This article explains the science, the timeline, and the claim framework.

Every veteran who's had a service-connected ankle, foot, or lower-extremity condition for more than a few years eventually notices the same thing: the pain doesn't stay where it started. The bad ankle starts to affect the knee. The knee starts to affect the hip. The hip starts to affect the low back. What was one problem becomes three or four.

If that describes you, you're not imagining it. You're experiencing what orthopedic and biomechanical scientists call compensatory kinetic chain loading — the well-documented process by which dysfunction at one lower-extremity joint alters gait mechanics and transmits abnormal stress to joints proximal (upward) and, sometimes, distal (downward) to the primary site of injury.

This isn't a fringe theory. It's foundational biomechanics, and it's why the VA's secondary service connection framework under 38 C.F.R. § 3.310 exists in the first place. This article walks through the science, the timeline, and how it maps onto VA secondary claims — so you understand what's happening in your body and what claim framework applies to your situation.

Table of Contents

• What Is the Kinetic Chain?
• What Happens When Gait Is Altered?
• The Upward Cascade: Knee, Hip, Low Back
• How Long Does It Take?
• The Bilateral Symmetry Principle
• What the Peer-Reviewed Literature Says
• The VA Framework: 38 CFR § 3.310 and Wallin v. West
• When It's "Just Pain": Saunders v. Wilkie
• Common Secondary Claim Pathways
• What Makes a Strong Secondary Claim Nexus Letter
• Frequently Asked Questions

What Is the Kinetic Chain?

The lower extremity — foot, ankle, knee, hip, pelvis, and low back — is not a set of independent joints. It is a coupled kinetic chain. Every joint in the chain influences the mechanical environment of every other joint during standing, walking, and running.

When the chain is functioning normally, the loads produced by ground contact during gait are absorbed and distributed evenly. The foot rolls through pronation and supination, the ankle dorsiflexes and plantar flexes, the knee flexes and extends with rotational coupling, the hip rotates and abducts, and the pelvis and lumbar spine make small, symmetric adjustments to maintain balance.

When one joint in the chain is compromised — by chronic instability, tendonitis, ligamentous laxity, arthritis, or pain avoidance — the whole chain reorganizes to compensate. That reorganization is what biomechanists call altered gait kinematics, and it is the mechanism by which a single service-connected lower extremity injury eventually damages the joints above and below it.

What Happens When Gait Is Altered?

An injured or unstable ankle changes the way you walk in several measurable ways:

• Antalgic gait — you shorten the time your weight rests on the painful side (called reduced stance time) and lengthen it on the healthy side. This shifts load across every joint upstream and on the opposite limb.
• Compensatory pronation or supination — the foot rolls inward or outward more than it should in an attempt to avoid loading the painful structure. This changes the alignment of the shin, which changes the alignment of the thigh, which changes the alignment of the pelvis.
• Impaired proprioception — the nervous system loses accurate positional feedback from the injured joint. Balance strategies shift to the hips and trunk, chronically overloading the hip abductors and low back stabilizers.
• Restricted range of motion at the ankle — reduced dorsiflexion, in particular, is compensated for by increased knee flexion and hip flexion during stance, changing joint loading angles at the knee and hip.
• Reduced activity levels — pain drives sedentary behavior, which reduces muscular support of the lower extremity and accelerates deconditioning that further compromises joint protection.

Each of these mechanisms is small on any given step. But an average adult takes 5,000 to 10,000 steps per day. Over years and decades of walking with compromised mechanics, small compensatory changes accumulate into structural damage at the adjacent joints.

For more on how a chiropractor evaluates altered gait mechanics and articulates the biomechanical case in a nexus letter, see Can a Chiropractor Write a Nexus Letter?

The Upward Cascade: Knee, Hip, Low Back

Once gait is altered by a foot or ankle disability, the mechanical consequences propagate upward through the kinetic chain. The specific pathologies that develop are predictable:

Knee

• Medial compartment stress and pain. Altered gait typically shifts weight-bearing to the inner portion of the knee joint. Over time this produces medial joint line tenderness, meniscal degeneration, and progression of medial compartment osteoarthritis. Prospective research has shown that dynamic loading at baseline predicts radiographic disease progression in the medial compartment.
• Patellofemoral pain. Altered tibial rotation and foot pronation change the tracking of the kneecap in its groove. This produces anterior knee pain, painful stair-climbing (a classic finding), and, over time, patellofemoral arthritis.
• Quadriceps weakness. Pain-driven reduced activity produces disuse atrophy of the thigh musculature. Weaker quads accelerate knee joint loading, feeding the cycle.

Hip

• Gluteal tendinopathy at the greater trochanter (greater trochanteric pain syndrome). When the ankle fails to provide a stable base of support, the frontal-plane demands on the hip abductor musculature (principally the gluteus medius and gluteus minimus) increase substantially. Chronic overload of these tendons produces the pathognomonic clinical picture of greater trochanter tenderness and hip abductor weakness.
• Femoroacetabular impingement (FAI) and intra-articular hip pain. Altered pelvic mechanics from long-standing altered gait change the way the femoral head sits in the acetabulum. Over years, this can produce cam- or pincer-type impingement patterns and intra-articular hip pain.
• Trochanteric bursitis. Chronic tendon overload frequently involves inflammation of the adjacent bursa. This is sometimes mislabeled as the primary problem when it is actually a downstream consequence of the tendinopathy.

Low Back

• Sacroiliac (SI) joint dysfunction. Asymmetric weight-bearing from altered gait chronically stresses the SI joints, producing unilateral low back pain that worsens with weight-bearing.
• Lumbar disc degeneration and lumbar spondylosis. Compensatory pelvic tilting and altered lumbar lordosis increase disc loading and facet joint contact pressure. Over years, this accelerates the natural aging process of the lumbar spine.
• Piriformis syndrome and sciatica. Compensatory hip external rotation from ankle dysfunction can chronically overload the piriformis muscle, occasionally producing referred sciatic-distribution pain.

Contralateral (Opposite) Limb Overuse

Contralateral compensation. When one side is chronically painful, the opposite limb is chronically overloaded. This is why unilateral primary conditions frequently produce bilateral secondary claims — the "good" leg wears out from having to do more of the work.

For veterans dealing with the aftermath of an ankle or foot service-connected condition, this cascade is the biomechanical explanation for the "everything hurts now" phenomenon that so many veterans describe.

How Long Does It Take?

The short answer: it varies, but expect years to decades before adjacent joint damage becomes clinically obvious.

The compensatory kinetic chain load is small on any single step. But it's cumulative. The typical timeline looks something like this:

• Years 1-3 after the primary injury: You adapt. Compensatory gait patterns develop. You may not notice any secondary symptoms yet — the body is compensating well and adjacent joints are still healthy enough to absorb the added load without complaint.
• Years 3-7: Subtle warning signs. Occasional knee soreness after long walks. Hip stiffness in the morning. Low back tightness at the end of the day. Most veterans dismiss these as normal aging.
• Years 7-15: Clinically documented adjacent joint pathology. Now the imaging shows medial compartment narrowing at the knee, or greater trochanter tenderness on exam, or facet arthropathy on the lumbar MRI. This is the window in which most secondary claims are filed.
• Years 15+: Advanced adjacent joint pathology. Sometimes multi-level. Sometimes bilateral. This is the profile that supports total-disability secondary claims and, in some cases, TDIU (total disability based on individual unemployability).

The takeaway: if it's been years since your primary lower-extremity injury and your knees, hips, or back are now hurting, that is not coincidence. It is the expected biomechanical consequence of walking on a compromised base of support for that long.

The Bilateral Symmetry Principle

Here's a subtlety that often makes or breaks a secondary claim: bilateral distribution of the primary condition typically produces bilateral distribution of the secondary condition.

When only one ankle is affected, the compensation pattern is asymmetric — the opposite limb takes more load, and the secondary condition often develops most severely on the contralateral (opposite) side. When both ankles are affected — which is the case for many veterans with bilateral service-connected ankle disabilities from years of running, marching, or jumping in service — the compensation is symmetric. Both knees, both hips, and the midline low back all take the increased load simultaneously.

If you have a bilateral primary condition and are developing bilateral secondary symptoms, that bilateral-to-bilateral correspondence is powerful evidence of the compensatory kinetic chain mechanism at work. It's not degenerative aging (which is usually asymmetric). It's the biomechanical fingerprint of your primary condition operating symmetrically through the chain.

What the Peer-Reviewed Literature Says

The kinetic chain mechanism I've described is not something I invented. It is thoroughly documented in the peer-reviewed orthopedic, biomechanical, and rehabilitation literature. Some of the foundational citations include:

• Chuter and Janse de Jonge (2012), Gait & Posture: "Proximal and distal contributions to lower extremity injury: a review of the literature." Establishes the core principle that dysfunction at one joint in the lower-extremity kinetic chain produces altered loading and injury risk at joints proximal to the primary site of dysfunction.
• Hertel (2002), Journal of Athletic Training: "Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability." Establishes that chronic ankle instability produces measurable, durable alterations in movement patterns that extend proximally through the kinetic chain.
• Andriacchi and Mündermann (2006), Current Opinion in Rheumatology: "The role of ambulatory mechanics in the initiation and progression of knee osteoarthritis." Establishes altered ambulatory mechanics as causally central to the initiation and progression of knee joint pathology.
• Powers (2003), Journal of Orthopaedic & Sports Physical Therapy: "The influence of altered lower-extremity kinematics on patellofemoral joint dysfunction." Establishes the propagation of altered lower-extremity kinematics from ankle to knee.
• Grimaldi and Fearon (2015), JOSPT: "Gluteal tendinopathy: Integrating pathomechanics and clinical features in its management." Establishes altered lower-limb biomechanics as a principal cause of gluteal tendinopathy at the greater trochanter.
• Neumann (2010), JOSPT: "Kinesiology of the hip: A focus on muscular actions." Establishes the mechanism by which distal ankle instability produces chronic overload of the hip abductor tendons and predisposes to gluteal tendinopathy.
• Miyazaki et al. (2002), Annals of the Rheumatic Diseases: "Dynamic load at baseline can predict radiographic disease progression in medial compartment knee osteoarthritis." Establishes prospectively that altered dynamic loading predicts the initiation and progression of knee pathology.

These are foundational, widely cited papers. When a well-drafted secondary-claim nexus letter cites this literature and applies it to a specific veteran's clinical picture, it is not stating opinion or speculation. It is applying settled biomechanical science to the facts of the case.

The VA Framework: 38 CFR § 3.310 and Wallin v. West

The VA's own regulatory framework explicitly recognizes the secondary service connection concept. 38 C.F.R. § 3.310 provides that a disability that is "proximately due to or the result of a service-connected disease or injury" is itself service-connected. Aggravation of a non-service-connected condition by a service-connected condition is also compensable, with the level of compensation reflecting the degree of aggravation.

The three-prong test for secondary service connection was articulated by the United States Court of Appeals for Veterans Claims in Wallin v. West, 11 Vet. App. 509 (1998):

1. A current disability. The claimed secondary condition must be currently diagnosed, or at minimum currently symptomatic with functional impairment (see the Saunders discussion below).
2. A service-connected disability. The primary condition — in this framework, your ankle, foot, or other lower-extremity condition — must be established as service-connected.
3. A nexus. There must be a medical connection between the primary and secondary conditions.

For a gait-compensation-driven secondary claim, the nexus is the biomechanical mechanism described in this article, supported by peer-reviewed literature, applied to the specific facts of your case. A well-drafted nexus letter walks the rater through each of the three prongs with objective evidence.

For more on the CFR 38 framework generally, see 38 CFR Explained: The Rulebook Every Veteran Should Know About Before They File a Claim.

2026 Update — §3.310 Causation Standard: Effective May 1, 2026, the VA updated the M-21-1 secondary service connection causation framework following Spicer v. McDonough. Nexus letters for secondary claims must now explicitly satisfy a "but for" standard under both 38 CFR §3.310(a) (causation) and §3.310(b) (aggravation). See The VA Changed the Rules on Secondary Claims: What the New 'But For' Standard Means for Your Nexus Letter (2026) for the full breakdown of what changed and how it affects kinetic chain secondary claims.

When It's "Just Pain": Saunders v. Wilkie

Many veterans who develop secondary joint pathology hear the same discouraging feedback: "It's just pain. There's no diagnosis, so there's no disability." That framing is legally outdated.

In Saunders v. Wilkie, 886 F.3d 1356 (Fed. Cir. 2018), the United States Court of Appeals for the Federal Circuit held that pain, in and of itself, can constitute a compensable disability under 38 U.S.C. § 1110 when the pain causes functional impairment of earning capacity.

Practically, this means that "bilateral knee pain" or "bilateral hip pain" — with documented functional impairment on walking, sleeping, or stair-climbing (as measured by the Patient Specific Functional Scale or similar tools) — is a compensable disability, even if the treating provider hasn't attached a pathological diagnosis like osteoarthritis or meniscal tear. If your VA physical therapist or primary care provider has documented pain plus functional impairment, that meets the current-disability element of the Wallin three-prong test.

Don't let a rater or a C&P examiner talk you out of a valid claim by saying "it's just pain." Saunders is settled law.

Common Secondary Claim Pathways

Based on my experience writing nexus letters for veterans, these are the most common gait-compensation-driven secondary claim pathways:

If your situation is in this table, your secondary claim has a biomechanically valid pathway. What remains is documenting the current diagnosis (or Saunders-qualifying pain with functional impairment), tying it to peer-reviewed literature, and articulating the mechanism for the rater in a well-drafted nexus letter.

What Makes a Strong Secondary Claim Nexus Letter

A strong secondary-claim nexus letter, in my view, does the following:

• Confirms the current diagnosis using contemporaneous treating-provider records (VA primary care, physical therapy, orthopedic consult, imaging).
• Identifies the service-connected predicate with the specific rating, effective date, and diagnostic code.
• Documents the temporal sequence — primary injury, then years of altered gait, then adjacent joint symptoms, then adjacent joint pathology. Temporal proximity between the primary condition's onset and the eventual adjacent joint findings is often the most persuasive evidentiary chain.
• Articulates the biomechanical mechanism clearly, in language a VA rater can understand.
• Cites peer-reviewed literature that establishes the mechanism as scientific consensus rather than provider opinion.
• Rules out competing etiologies — proactively addresses age-related degeneration, obesity, non-service-connected trauma, or other alternative explanations.
• Applies the correct legal framework — 38 C.F.R. § 3.310, Wallin v. West three-prong test, Buchanan v. Nicholson for lay observation, Saunders v. Wilkie when pain alone constitutes disability.
• Concludes with the "at least as likely as not" opinion in the precise language raters are trained to look for.

The letter also needs to be written by a medical provider whose training and licensure are within scope for the claim. For most gait-compensation secondary claims involving the lower extremity kinetic chain, a chiropractor whose training is squarely in musculoskeletal biomechanics is well within scope. For claims involving intra-articular imaging findings or surgical candidacy, an orthopedic surgeon's opinion may carry additional weight.

For more on what separates a strong nexus letter from a weak one, see What Makes an Effective Nexus Letter.

Frequently Asked Questions

My ankle injury is service-connected but it's been 20 years. Is it too late to file a secondary claim for my knee?

No. Secondary service connection has no time limit. Some of the strongest secondary claims are filed 15, 20, or 30 years after the primary injury, when the adjacent joint pathology has become clearly documented. The longer you have been ambulating on a compromised base of support, the more the cumulative biomechanical damage supports the claim.

The VA denied my secondary claim because "there is no medical evidence connecting the two conditions." What now?

That denial almost always reflects the absence of a properly drafted nexus letter — not the absence of a valid claim. Under the framework described in this article, virtually every gait-compensation-driven adjacent joint claim has a valid biomechanical pathway. A supplemental claim or Higher-Level Review supported by a nexus letter that cites the peer-reviewed literature and applies the Wallin three-prong test to your specific facts is the typical path forward. For more on the denial-and-appeal process, see Why VA Claims Get Denied (and How to Fix It).

My knee/hip/back MRI shows "age-related degeneration." Doesn't that defeat my secondary claim?

Not necessarily. Age-related changes and gait-driven degeneration coexist. The relevant question under 38 C.F.R. § 3.310 is whether your service-connected primary condition has caused or aggravated beyond its natural progression the current adjacent joint pathology. A well-drafted nexus letter addresses age-related contribution honestly, then explains why the primary condition has aggravated the natural progression — often through the bilateral-symmetry principle discussed above, or through documented onset timing, or through the specific pattern of findings (e.g., disproportionately advanced medial compartment involvement in a young veteran).

Does obesity or diabetes complicate the secondary claim?

Sometimes, but not fatally. If obesity or diabetes are themselves secondary to a service-connected condition (for example, medication-associated weight gain from SSRI treatment of service-connected depression, or pain-driven inactivity), they can be secondary predicates in a multi-step framework recognized by VAOPGCPREC 1-2017 (obesity as an intermediate step). A well-drafted nexus letter addresses these factors explicitly rather than pretending they don't exist.

I'm not filing yet. Should I still get a nexus letter?

If you're not sure whether to file, a free consultation with a nexus letter provider can help you decide. I offer a free records review before any invoicing — if I look at your records and don't think a nexus letter will move your claim, I say so before any money changes hands. See Why I Offer Free Nexus Letter Consultations.

Can a chiropractor write this kind of nexus letter?

Yes. Gait compensation and adjacent joint damage from lower extremity kinetic chain dysfunction are squarely within a chiropractor's scope of training and practice. Most of the peer-reviewed literature cited above is authored by physical therapists, biomechanists, and orthopedic surgeons, but the underlying subject matter — musculoskeletal biomechanics — is core chiropractic training. For more on this, see Can a Chiropractor Write a Nexus Letter?

What's the difference between a nexus letter and a DBQ for a secondary claim?

A nexus letter provides the medical opinion connecting the primary and secondary conditions. A DBQ (Disability Benefits Questionnaire) documents the severity of the secondary condition for rating purposes. Most secondary claims benefit from both — a nexus letter to establish service connection, and a DBQ (either from your VA C&P exam or from an independent examiner) to establish the rating percentage. For more, see DBQ vs Nexus Letter: What's the Difference and Why Both Matter for Your VA Claim.

If You're Considering a Secondary Claim

Three things you can do this week:

1. Get a current diagnosis on the record. If your knee, hip, or back is symptomatic, get in to your VA primary care or physical therapy. A treating-provider note that documents your current condition (even as "pain" plus functional impairment) is the foundation of any claim under the framework described here.
2. Write a personal statement describing when your adjacent joint symptoms started, what makes them worse, and how they relate to your existing service-connected primary condition. Your own words are competent evidence under Buchanan v. Nicholson, and a written personal statement significantly strengthens the claim file.
3. Talk to a direct medical provider who can review your records and give you an honest read on whether a nexus letter will move your case. I offer that consultation free, directly with me, by phone or email — domestic or international. If I don't think I can help, I'll tell you before you spend a dime.

The kinetic chain is real. Gait compensation causes durable damage to adjacent joints over time. The VA's own secondary service connection framework was written precisely to compensate veterans for this cascade. If you have a service-connected lower extremity condition and are now dealing with knee, hip, or back symptoms, the science is on your side.

This article is for informational purposes only and is not legal or medical advice. It is intended to help veterans understand the biomechanical basis of secondary service connection claims for lower extremity kinetic chain conditions. Always verify any provider's credentials and consult with your treating providers about your specific medical situation.