Secondary Conditions to Knee Pain

Knee problems rarely stay in the knee. You favor one leg, shorten your stride and take stairs differently, and other joints take on load they were not built to carry alone. Under 38 CFR § 3.310, a condition caused or worsened by your service-connected knee is service connected too, and it is rated under its own diagnostic code. This page covers what you can claim, the research behind each link, which claims to file first, and how the ratings combine, including the bilateral factor.

What can you claim secondary to a knee condition?

Any condition a doctor can tie to your knee, with reasoning, can be claimed. In the Board's 2021 to 2026 decisions the most common were these.

• The low back. See back and back secondary to knee.
• The hip. See hip and hip secondary to knee.
• Sleep apnea.
• The ankle and foot, such as flat feet and plantar fasciitis.
• The shoulder.
• Mental health conditions, such as depression and anxiety, which the Board often writes as an acquired psychiatric disorder.
• The neck and the spinal discs. See cervical spine and degenerative disc disease.
• GERD, usually through pain medication.

The Board section further down lists every condition claimed secondary to the knee with enough rulings to show, with its count and grant rate. The other knee is often claimed as well; it is covered below with the hip.

How secondary service connection works for a knee condition

VA grants a secondary claim in two ways under 38 CFR § 3.310.

• Caused by. Your service-connected knee caused the condition, at least as likely as not.
• Aggravated by. The condition is worse because of your knee, meaning it would be less severe but for the knee condition (M21-1 V.ii.2.D). VA rates only the part above the condition's baseline before the aggravation.

The text of § 3.310(b) still tells VA to subtract "natural progress," but VA's current claims manual (M21-1 V.ii.2.D, revised after Spicer v. McDonough) no longer applies that part, and the worsening does not have to be permanent. VA still needs a baseline shown by medical evidence, and it rates the difference between that baseline and the current level.

The file needs a service-connected knee, a current diagnosis of the secondary condition, and a medical opinion linking the two. For knee chains the opinion has to identify the mechanism, address the time course and rule out other causes; a bare "more likely than not" without reasoning carries little weight. An opinion that answers only the "caused by" question and skips aggravation is inadequate (El-Amin v. Shinseki, 26 Vet. App. 136 (2013)).

Some chains run through weight. VA does not treat obesity as a disability on its own, but VA's General Counsel (VAOPGCPREC 1-2017) allows it to be a middle step when the knee condition, or the inactivity it forces, led to weight gain, the weight gain was a substantial factor in causing the claimed condition, and the condition would not have happened without it. The Court of Appeals for Veterans Claims built on that framework in Walsh v. Wilkie, 32 Vet. App. 300 (2020).

The most common secondary conditions to a knee condition

The low back and the spinal discs

The research term is "knee-spine syndrome." In a study of 205 people with knee arthritis (Iijima and colleagues, Arthritis Care & Research, 2020), 45 showed varus thrust, an outward bowing of the knee as weight lands on it, and they had a 3.6-fold higher risk of moderate-to-severe low back pain. The authors read this as support for a mechanical link between the knee and the back. The study shows an association, not which came first.

The opinions that win describe altered gait, favoring one side, the shift of load over years, and the time from the knee problem to the back symptoms, then explain why the back comes from the knee rather than only from age, work, weight or a separate injury. "Back pain is secondary to knee pain" is not enough. The low back is rated under the spine formula in 38 CFR § 4.71a on forward flexion: 10 percent above 60 degrees up to 85, 20 percent above 30 up to 60, and 40 percent at 30 degrees or less. Degenerative disc disease without nerve root compression uses the same formula under Diagnostic Code 5242. See back secondary to knee.

The hip and the other knee

When one knee hurts, the other leg works harder. In a lab study of 16 people with arthritis in one knee and 16 healthy adults (Liu and colleagues, Annals of Biomedical Engineering, 2023), climbing stairs put higher load and muscle force on the unaffected leg, with differences at the ankle, knee and hip. The authors note that most one-sided knee arthritis becomes two-sided within 10 years, and that leaning on the good side may harm it. A walking study of people with arthritis in one hip, knee or ankle (Campbell and colleagues, Journal of Orthopaedic Research, 2025) found the unaffected leg, especially the ankle, produced more power to make up the loss, and the authors suggest those joints may be affected over time. Both studies measure shifted load, not new disease, so the opinion has to connect them to your diagnosis and timeline.

Hip flexion is rated under Diagnostic Code 5252, from 10 percent at 45 degrees to 40 percent at 10 degrees. See hip secondary to knee.

Sleep apnea

The usual path is inactivity and weight gain. In a study of 1,922 adults with or at risk for knee arthritis who wore activity monitors (Chang and colleagues, Osteoarthritis and Cartilage, 2020), 44.1 percent of men and 22.2 percent of women met federal activity guidelines, and frequent knee symptoms were tied to not meeting them. A population cohort (Peppard and colleagues, JAMA, 2000) found a 10 percent weight gain predicted about a 32 percent rise in the apnea-hypopnea index and a sixfold increase in the odds of moderate-to-severe sleep-disordered breathing. Long-term opioid use is the other argument; the back cause hub covers that research. Sleep apnea that requires a CPAP rates 50 percent under Diagnostic Code 6847.

The ankle, the foot and the shoulder

The Campbell study above found the ankle on the unaffected side did much of the compensating, which fits an ankle claim on the opposite side. Ankle motion is rated under Diagnostic Code 5271 at 10 percent for moderate and 20 percent for marked limitation. I found no study that followed foot problems or shoulder problems developing from a knee condition; a shoulder claim usually argues years of leaning on a cane or crutches, and the opinion has to carry it with your history.

Depression and anxiety

The evidence is mixed. A 2025 meta-analysis of chronic pain (Aaron and colleagues, JAMA Network Open) found clinical depression symptoms in 29.1 percent of people with osteoarthritis and anxiety symptoms in 17.5 percent. An earlier meta-analysis of 49 studies (Stubbs and colleagues, Age and Ageing, 2016) found about one-fifth of people with osteoarthritis had depression or anxiety symptoms, but could not show the rate was higher than in people without it. The opinion should tie your symptoms to the knee's effect on your work and daily life. All of your mental health diagnoses share one rating under the mental disorders formula.

The neck

I found no study showing that a knee condition causes a neck condition. This claim rests on the examiner's reasoning about posture and gait, so it is one of the harder chains to win.

GERD

The argument is the anti-inflammatory pain relievers (NSAIDs) many veterans take for knee pain. A meta-analysis of 102 population studies (Eusebi and colleagues, Gut, 2018) found reflux symptoms more common in NSAID or aspirin users, with an odds ratio of 1.44, and the authors called the association modest. Your pharmacy record showing long-term NSAID use is central to this claim. GERD is rated under Diagnostic Code 7206; the GERD page covers the current criteria.

Which secondary claims to file first

Three questions sort the claims worth filing.

1. Is there a current diagnosis? No diagnosis, no claim. A back or hip claim needs imaging or exam findings; sleep apnea needs a sleep study.
2. Can it be rated on its own? The back, hip, other knee, ankle and sleep apnea have their own ratings. A second mental health diagnosis does not add a second rating.
3. Will a doctor explain the link? Gait-based claims live or die on the opinion. If no clinician will describe how your walking changed and when, start there.

For most veterans the back and the hip come first, because they are the most common chains and carry their own ratings. Raven Nexus organizes your records and the relevant research into a draft your doctor can review, and buddy letters can show when your limp or cane use began.

How secondary ratings combine with a knee rating

VA combines ratings under 38 CFR § 4.25, largest first, and each smaller rating takes its share of what remains. When joints in both legs are rated, 38 CFR § 4.26 adds a step first: VA combines the right and left leg ratings, adds 10 percent of that value, and treats the result as one rating. The two legs do not have to share a joint; a right knee and a left hip count.

Take a right knee at 20 percent (flexion limited to 30 degrees) and a low back at 20 percent secondary to it. They combine to 36, which VA rounds to 40 percent. Now add the left knee at 10 percent, secondary to the right. The two knees combine to 28, and the bilateral factor adds 2.8, which gives about 31. That 31 and the back's 20 combine to about 45, which VA rounds up to 50 percent. A 10 percent claim moved the total by 10 points because it brought in the bilateral factor.

Secondary conditions also count toward TDIU. For its percentage test, 38 CFR § 4.16(a) treats disabilities of one or both legs, including the bilateral factor, as one disability.

Questions veterans ask about secondary conditions to knee pain

What conditions are secondary to a knee condition?

The most common in Board decisions are the low back, the hip, sleep apnea, the ankle and the foot. Any condition a doctor can tie to your knee with reasoning can be claimed.

Can back pain be secondary to knee pain?

Yes, when a doctor explains how the knee changed your gait and how that led to or worsened the back condition. Research on "knee-spine syndrome" supports the link, but it shows association, so the opinion has to apply it to your timeline.

Can hip pain be secondary to a knee condition?

Yes. Studies show the other leg and its hip take on more load when one knee hurts, and the opinion has to connect that to your hip diagnosis.

Does the bilateral factor apply if my other knee is secondary to the first?

Yes, if both knees have compensable ratings. VA combines the two, adds 10 percent of that value, and then combines the result with your other ratings.

Can sleep apnea be secondary to a knee injury?

It can, usually through inactivity and weight gain that the knee caused. VA's General Counsel allows weight to be a middle step when the opinion shows it was a substantial factor.

Sources

• 38 CFR § 3.310, secondary service connection; M21-1 V.ii.2.D, aggravation of a nonservice-connected disability by a service-connected one; Spicer v. McDonough (Federal Circuit).
• 38 CFR § 4.71a, General Rating Formula for Diseases and Injuries of the Spine and Diagnostic Codes 5242, 5252, 5260 and 5271; 38 CFR § 4.97, Diagnostic Code 6847; 38 CFR § 4.114, Diagnostic Code 7206; 38 CFR § 4.130.
• 38 CFR § 4.25, combined ratings; 38 CFR § 4.26, bilateral factor; 38 CFR § 4.16, TDIU.
• VA General Counsel Precedent Opinion 1-2017 (VAOPGCPREC 1-2017), obesity as an intermediate step; Walsh v. Wilkie, 32 Vet. App. 300 (2020).
• El-Amin v. Shinseki, 26 Vet. App. 136 (2013), an opinion must address aggravation.
• Iijima H, Suzuki Y, Aoyama T, et al. Relationship Between Varus Thrust During Gait and Low Back Pain in Individuals With Knee Osteoarthritis. Arthritis Care & Research. 2020;72(9):1231-1238. PMID 31254449.
• Liu S, Amiri P, McGregor AH, et al. Bilateral Asymmetry in Knee and Hip Musculoskeletal Loading During Stair Ascending/Descending in Individuals with Unilateral Mild-to-Moderate Medial Knee Osteoarthritis. Annals of Biomedical Engineering. 2023;51(11):2490-2503. PMID 37482575.
• Campbell J, Schmitt D, Sands LP, et al. Unilateral Single Joint Arthritis Changes Joint Power in Unaffected Joints. Journal of Orthopaedic Research. 2025;43(7):1269-1274. PMID 40223337.
• Chang AH, Song J, Lee J, et al. Proportion and associated factors of meeting the 2018 Physical Activity Guidelines for Americans in adults with or at risk for knee osteoarthritis. Osteoarthritis and Cartilage. 2020;28(6):774-781. PMID 32200050.
• Peppard PE, Young T, Palta M, et al. Longitudinal study of moderate weight change and sleep-disordered breathing. JAMA. 2000;284(23):3015-3021. PMID 11122588.
• Aaron RV, Ravyts SG, Carnahan ND, et al. Prevalence of Depression and Anxiety Among Adults With Chronic Pain: A Systematic Review and Meta-Analysis. JAMA Network Open. 2025;8(3):e250268. PMID 40053352.
• Stubbs B, Aluko Y, Myint PK, et al. Prevalence of depressive symptoms and anxiety in osteoarthritis: a systematic review and meta-analysis. Age and Ageing. 2016;45(2):228-235. PMID 26795974.
• Eusebi LH, Ratnakumaran R, Yuan Y, et al. Global prevalence of, and risk factors for, gastro-oesophageal reflux symptoms: a meta-analysis. Gut. 2018;67(3):430-440. PMID 28232473.
• Board figures on this page: Claim Raven's read of every Board decision from 2021 to 2026 that it holds.