A service-connected knee rarely acts alone. Years of favoring it overload the opposite knee, and the altered gait can reach the hips and back. Under 38 CFR 3.310, those can be claimed as secondary — and when both knees or legs end up service-connected, the bilateral factor (38 CFR 4.26) adds value beyond the raw percentages.
Straight talk first
Bodies compensate. Limp on a bad knee long enough and the other leg, the hips, and the lower back start paying for it. VA recognizes that chain — but only if you claim the downstream joints and show the link. The bonus most veterans don't know about: when you get both knees (or both legs) service-connected, VA applies a bilateral factor that bumps the math in your favor. So the second knee can be worth more than its number suggests.
This is the knee-specific cut of the framework on VA secondary conditions.
The links veterans commonly pursue
Each is a starting point to investigate with a provider, not a guaranteed grant:
- Opposite knee secondary to the service-connected knee — overcompensation from favoring the bad side.
- Hip secondary to the knee — altered mechanics traveling up the leg.
- Back condition secondary to the knee — an antalgic gait loading the spine.
- Depression or anxiety secondary to chronic knee pain and lost mobility.
Use the Secondary Conditions Finder to see how your rated knee commonly links.
What you have to prove (38 CFR 3.310)
- A current diagnosis of the secondary joint or condition.
- An already service-connected knee as the primary.
- A medical nexus — an opinion that the knee "at least as likely as not" caused or aggravated the secondary, ideally explaining the gait/overcompensation mechanism.
The mechanics of documenting and submitting this are in how to file your own claim.
The bilateral factor — the knee math bonus
When disabilities affect both lower extremities (e.g., both knees), 38 CFR 4.26 adds a bilateral factor: VA combines the paired ratings, adds an extra percentage of that combined value, and then combines with your remaining ratings. It's easy to under-count, so once a second knee is in play, run it through the VA Combined Rating Calculator to see the real effect.
How knee conditions are rated
Knee disabilities are rated under 38 CFR 4.71a based on limitation of motion, instability, arthritis, and related factors — and instability can sometimes be rated separately from limitation of motion for the same knee. Each rating combines using VA math.
Key takeaways
- A service-connected knee commonly drives secondaries in the opposite knee, hip, and back.
- It runs through 38 CFR 3.310 — diagnosis, the knee as primary, and a gait-based nexus.
- The bilateral factor (4.26) adds value when both knees/legs are service-connected.
- Use the calculator — knee math (separate ratings + bilateral factor) is easy to undercount.
Frequently asked questions
- Can my other knee be secondary to my service-connected knee?
- Often, yes. Years of favoring a bad service-connected knee can overload the opposite knee. Veterans commonly claim the opposite knee as secondary under 38 CFR 3.310 — with a current diagnosis, the service-connected knee as primary, and a medical opinion explaining the overcompensation.
- What's the bilateral factor and why does it matter for knees?
- When both knees (or both legs) are service-connected, 38 CFR 4.26 adds an extra factor to the combined rating for the paired disabilities before combining with the rest. So getting the second knee service-connected can be worth more than the percentage alone suggests.
- Can a knee condition affect my back or hip?
- Yes. An altered or antalgic gait from a service-connected knee can be claimed as causing or aggravating a hip or back condition. The link is medical, so a nexus opinion explaining the gait mechanism carries it. See our back-conditions guide for the spine side.
- How are knee conditions rated?
- Knee disabilities are rated under VA's musculoskeletal schedule (38 CFR 4.71a) based on factors like limitation of motion, instability, and arthritis — and instability can sometimes be rated separately from limitation of motion. Each rating then combines using VA math.
Sources
- 38 CFR 3.310 — secondary service connection (caused or aggravated): https://www.ecfr.gov/current/title-38/chapter-I/part-3/subpart-A/section-3.310
- 38 CFR 4.26 — the bilateral factor: https://www.law.cornell.edu/cfr/text/38/4.26
- 38 CFR 4.71a — schedule of ratings, musculoskeletal system (knee): https://www.law.cornell.edu/cfr/text/38/4.71a
- VA — how VA decides service connection: https://www.va.gov/disability/eligibility/
