Back Pain Secondary to Knee Pain: VA Disability Claim Guide

Overview

Low back conditions are a common secondary claim for veterans with a service-connected knee condition. The two problems frequently occur together: in the Osteoarthritis Initiative, 57.4% of 1,389 adults with symptomatic knee osteoarthritis reported low back pain, and those with back pain also reported worse knee pain (Suri et al., 2010). Clinicians sometimes call the combination “knee-spine syndrome.”

Co-occurrence is not the same as causation, and back pain is common in the general population. Under 38 CFR § 3.310, you need medical evidence that your knee condition is at least as likely as not the cause of your back condition, or that it made a back condition worse. The claim rises or falls on how specifically the medical opinion ties your knee to your back.

How Back Pain Is Connected to Knee Pain

Altered gait and loading. A painful, stiff, or unstable knee changes stride, stance time, and how weight is shared between the legs. A clinician can explain how a documented limp or antalgic gait placed repetitive asymmetric stress on the lumbar spine over time.

Varus thrust. In a study of 205 people with knee osteoarthritis, those whose knee visibly shifted outward during walking (varus thrust) had a 3.6-fold higher likelihood of moderate-to-severe low back pain (Iijima et al., 2020). The authors describe this as support for a biomechanical knee-spine link. It is an association in one study, but it gives the examiner a specific finding to look for.

Posture and leg length. A knee that cannot fully straighten, or a knee replacement or cartilage loss that changes leg length, can change pelvic position and lumbar posture. If your records document a flexion contracture or measured leg length difference, that is concrete support for the mechanism.

Weight gain from inactivity. Knee pain can limit exercise and lead to weight gain. A meta-analysis found obesity associated with higher rates of low back pain, including chronic low back pain (Shiri et al., 2010). VA does not treat obesity itself as a disability, but VA’s General Counsel has held that obesity can be an “intermediate step” for secondary service connection (VAOPGCPREC 1-2017). The evidence must show the knee caused or worsened the weight gain, the weight gain was a substantial factor in the back condition, and the back condition would not have happened without it.

Evidence Requirements

• Current lumbar diagnosis. For example lumbosacral strain, degenerative disc disease, facet arthritis, or stenosis, with imaging if your doctor ordered it.
• Service-connected knee documentation. Your rating decision for the knee.
• Gait evidence. PT or clinic notes describing an antalgic gait, limp, varus thrust, flexion contracture, leg length difference, or brace or cane use.
• Timeline. Records showing back symptoms started or worsened after the knee condition.
• Medical nexus opinion. An opinion that the back condition is at least as likely as not caused or aggravated by the knee condition, explaining the mechanism and addressing other likely causes such as age, prior back injuries, or heavy labor.
• Treatment records and lay statements. Back treatment, and statements from you and others about the limp, when back pain began, and how it limits bending, lifting, sitting, and work.

Rating Criteria for Back Pain

The lumbar spine is rated under the General Rating Formula for Diseases and Injuries of the Spine (DCs 5235-5243), with or without symptoms such as pain, stiffness, or aching. DC 5237 covers lumbosacral strain; DC 5242 covers degenerative arthritis and degenerative disc disease; DC 5243 is intervertebral disc syndrome (IVDS).

• 10% — Forward flexion greater than 60 but not greater than 85 degrees; or combined range of motion greater than 120 but not greater than 235 degrees; or muscle spasm, guarding, or localized tenderness not resulting in abnormal gait or abnormal spinal contour; or vertebral body fracture with loss of 50% or more of the height
• 20% — Forward flexion greater than 30 but not greater than 60 degrees; or combined range of motion not greater than 120 degrees; or muscle spasm or guarding severe enough to result in an abnormal gait or abnormal spinal contour such as scoliosis, reversed lordosis, or abnormal kyphosis
• 40% — Forward flexion of 30 degrees or less; or favorable ankylosis of the entire thoracolumbar spine
• 50% — Unfavorable ankylosis of the entire thoracolumbar spine
• 100% — Unfavorable ankylosis of the entire spine

Normal thoracolumbar motion is 90 degrees of flexion, 30 degrees each of extension, lateral flexion, and rotation, for a combined 240 degrees.

Note (1): Associated objective neurological abnormalities, such as radiculopathy or bowel or bladder impairment, are rated separately under the appropriate diagnostic code.

IVDS alternative: When the diagnosis is IVDS (disc herniation with compression or irritation of the adjacent nerve root), VA can instead rate on incapacitating episodes, meaning bed rest prescribed by a physician and treatment by a physician: 10% for at least 1 week, 20% for at least 2 weeks, 40% for at least 4 weeks, and 60% for at least 6 weeks in the past 12 months, whichever method gives the higher result.

Functional loss: Under 38 CFR §§ 4.40, 4.45, and 4.59, VA considers pain, weakness, fatigability, and flare-ups. Pain alone does not automatically count as lost motion, so the examiner should describe how pain actually limits you, including an estimate of motion during flare-ups.

Nexus Letter Tips

Who should write it: Any qualified clinician can provide the opinion; VA does not require a specialist. VA weighs the opinion on its reasoning and on whether it rests on accurate facts. A physician who has examined both your knee and your back is well placed. Chiropractic records can help document the back condition.

What it should include:

1. Confirmation of a records review and examination
2. The lumbar diagnosis and supporting findings
3. The knee condition and the documented gait or posture changes it caused
4. The specific mechanism in your case, tied to entries in your records
5. How other risk factors (age, occupation, prior back injuries) were weighed
6. If the back condition existed before the knee condition, how the knee made it worse beyond its natural progress
7. The conclusion in VA’s standard: “at least as likely as not” (50% or greater probability)

Research can support the reasoning, but VA does not require the opinion to cite studies.

C&P Exam Tips

The examiner will usually complete the Back (Thoracolumbar Spine) Conditions DBQ, which covers range of motion, pain, flare-ups, repetitive use, muscle spasm and guarding (including whether it causes an abnormal gait or spinal contour), radiculopathy, and IVDS.

• Report pain where it starts during flexion, extension, side bending, and rotation.
• Describe typical days and flare-ups accurately. How often flare-ups happen, how long they last, and what you cannot do during them. The examiner should estimate your motion during a flare-up.
• Explain the knee connection with dates. When the knee problem began, when you started limping, and when back pain began.
• Report leg symptoms. Radiating pain, numbness, tingling, or weakness in the legs should be documented so radiculopathy can be evaluated.
• Walk as you normally do and bring any cane or brace you use.
• Report incapacitating episodes only if a physician prescribed bed rest, and bring the records.

Aggravation

If you had back problems before your knee condition, the claim can be based on aggravation under 38 CFR § 3.310(b). VA only concedes aggravation when medical evidence establishes the back’s baseline severity, either before the aggravation or through the earliest medical evidence after it began. VA rates the increase above that baseline, minus natural progression. For example, if the back was 10% before the knee worsened it and is 40% now, the secondary award reflects the difference rather than the full 40%.

Impact on Combined Rating

Ratings combine under 38 CFR § 4.25. See VA math for the full method.

Example — knee plus back: A veteran has 30% for the right knee and receives 20% for a lumbar strain secondary to it. 30 and 20 combine to 44, which rounds to 40%.

Example — adding radiculopathy: The same veteran is later rated 20% for right-leg and 20% for left-leg radiculopathy secondary to the back.

1. The right knee (30%) and both legs’ radiculopathy (20% and 20%) are all disabilities of the legs, so they go into the bilateral factor calculation (38 CFR § 4.26). 30 and 20 combine to 44; 44 and 20 combine to 55.
2. Add 10% of 55 (5.5): 60.5, treated as 61.
3. Combine 61 with the 20% back: 61 + (20% of 39) = 68.8, treated as 69.
4. 69 rounds to a final 70%.

Radiculopathy ratings depend on severity under DC 8520 (10% mild, 20% moderate, 40% moderately severe, 60% severe with marked muscular atrophy, 80% complete paralysis). There is no typical rating; it depends on the nerve findings. See the radiculopathy guide for details.

For personalized guidance on your VA disability claim, consult a VA-accredited VSO, attorney, or claims agent.