Short answer: Yes. An irritated nerve root in the lower back can cause pain in the knee even when the knee itself is perfectly healthy. Classic sciatica (from the L4 to S1 nerve roots) tends to show up behind or on the outside of the knee and down the leg. Irritation higher up, at the L3 and L4 levels, can produce pain at the front or inside of the knee. Clues that your knee pain is coming from your back include no knee injury, pain that doesn’t change much when you move the knee, and back, buttock, or thigh symptoms that come along with it.
This is one of the most common “hidden” causes of knee pain I see, and one of the most frustrating for the people who have it. They’ve had their knee X-rayed. Maybe an MRI. Maybe an injection. Nothing helps much, because nobody has looked at the spine.
Over about twelve years of treating patients at Balanced Flow, the clinic I founded here in Chicago, I’ve learned to check the back on almost every knee that doesn’t make sense. Here’s why, and how to tell if it’s happening to you.
How can a back problem cause knee pain?
Your brain doesn’t receive pain from “the knee.” It receives signals from nerves, and it maps those signals onto the part of the body that nerve normally serves. The nerves that supply the knee and the skin around it start in your lower back. If one of those nerve roots gets irritated where it exits the spine — by a disc bulge, arthritic narrowing (stenosis), or inflammation — the brain can read that irritation as pain in the knee. The knee is fine. The wire running to it is not.
This is called referred or radicular pain, and it’s why knee pain from the back often feels deep, hard to pinpoint, or “not quite like a joint.”
Is it really sciatica, or something else?
Here’s a distinction most articles skip. “Sciatica” technically refers to the sciatic nerve, which comes from the L4 through S3 nerve roots and runs down the back of the thigh. It splits into its two main branches just above the knee. So true sciatica tends to produce pain behind the knee, on the outside of the knee, and down into the calf, shin, or foot.
But people (and plenty of providers) use “sciatica” loosely for any nerve pain that travels from the back into the leg. Pain at the front or inside of the knee usually comes from higher nerve roots — L3 and L4 — which feed the femoral nerve and its branch, the saphenous nerve. In a study of patients with confirmed upper lumbar disc herniations, 80% of those with an L3 nerve root problem had pain or numbness at the inside of the knee, while L2 problems produced pain in the thigh just above the knee.1
Whatever you call it, the practical point is the same: a lower back problem can absolutely show up as knee pain, at almost any spot around the knee.
What does knee pain from the back feel like?
These are the patterns that make me look at the spine:
No injury, and nothing on the knee exam. The knee moves well, isn’t swollen, and pressing on it or stressing the ligaments doesn’t reproduce the pain.
Burning, tingling, numbness, or electric pain. Joint pain is usually achy and tied to movement. Nerve pain often has a different character, and sometimes comes with pins and needles or a patch of numb skin.
Pain that travels. It may start in the buttock, groin, or thigh and run to the knee, or continue below it.
It changes with back positions. Sitting, bending, or standing for a long time aggravates it; changing position or lying down eases it — even though you didn’t move your knee.
Weakness that doesn’t match a knee problem. Trouble with stairs because your thigh feels weak, a foot that catches, or a reflex that’s diminished.
You also have back pain — or used to. Not always, though. Nerve-related leg pain can occur with little or no back pain, which is exactly why it gets missed.
What else can make knee pain come from somewhere other than the knee?
The hip is the other big one. Hip arthritis can refer pain well down the leg. In one study of patients waiting for a hip replacement, 47% had pain below the knee — following the path of the saphenous nerve — even though most orthopedic trainees surveyed believed hip pain doesn’t travel past the knee.2 So a thorough exam checks both the hip and the back.
It can also be more than one thing at once. Knee arthritis, hip arthritis, and lumbar stenosis often coexist. In a 2025 study of patients having surgery for lumbar spinal stenosis, more than half (55.4%) also had severe hip or knee arthritis, and those patients reported worse back and leg pain a year after surgery.3 That’s why I don’t love single-joint thinking. A painful knee in a 60-year-old might be part knee, part hip, part spine — and the plan has to address all three.
Why don’t knee scans catch it?
Because they’re looking in the wrong place — and even in the right place, imaging doesn’t always line up with symptoms. Many adults have some knee arthritis on X-ray, and a systematic review found that the relationship between what the X-ray shows and whether the knee actually hurts is weak and inconsistent.4 So it’s easy for a knee X-ray to show “a little arthritis,” for that to get blamed, and for the real source in the back to go unnoticed. If your treatment hasn’t matched your expectations, that mismatch is worth questioning.
How do you tell if your knee pain is coming from your back?
At Balanced Flow, when a knee doesn’t add up, we run through a few checks:
A full knee exam to see whether the knee itself reproduces the pain.
Back and hip movement testing — does bending, extending, or rotating your spine, or loading your hip, change the knee symptoms?
Nerve tension tests like the straight leg raise, slump test, and femoral nerve stretch test, which gently tension the nerves to see if they reproduce your knee pain. In the upper lumbar herniation study above, the femoral nerve stretch test was positive in over 90% of patients.1
A neurological screen — reflexes, strength, and sensation mapped to specific nerve roots.
If the pattern points to the spine, imaging of the lower back may be appropriate. Often, though, the clinical picture is clear enough to start treatment and watch how the knee responds.
How do you treat knee pain caused by the lower back?
You treat the source. That usually means:
Calming the irritated nerve. Positions and movements that take pressure off the nerve root, plus activity modification for a short period — not bed rest.
Hands-on care for the spine and pelvis. Spinal manipulation can help nerve-related leg pain. In a randomized double-blind trial of patients with acute back pain and sciatica from disc protrusions, 55% of those receiving real chiropractic manipulation became free of radiating leg pain, compared with 20% who received simulated manipulation.5 (If you’re curious how chiropractic care fits into knee problems more broadly, see can a chiropractor help with knee pain?)
Nerve mobility work. Gentle “nerve gliding” exercises that help the nerve move freely again.
Core, hip, and leg strengthening. To unload the spine and restore any strength the irritated nerve has cost you.
Addressing the knee and hip too, if they’re involved. Because they often are.
When the back is the driver, it’s common for knee pain to ease as the spine settles — sometimes faster than people expect.
We’re also not opposed to regenerative therapy at Balanced Flow. If a spine, hip, or knee isn’t responding to physical therapy the way it should, or we want to accelerate recovery, it can be a valuable addition to the plan — layered on top of correcting the mechanics, not in place of it.
When is knee and leg pain an emergency?
Get urgent medical care if leg pain comes with numbness in the groin or inner thighs (saddle area), new loss of bladder or bowel control, rapidly worsening weakness in one or both legs, or fever with severe back pain. These can signal serious nerve compression or infection and need immediate attention.
The bottom line
If your knee hurts and nobody can find anything wrong with the knee, look higher. The lower back and the hip are two of the most common — and most commonly missed — sources of knee pain. Find the real source, treat that, and the knee often takes care of itself.
If you’re in Chicago and your knee pain hasn’t responded the way it should, book a consult at Balanced Flow. We’ll check the whole chain — knee, hip, and spine — and build a plan around what we actually find. For the full picture on knee pain without a clear injury, read what can cause knee pain without injury.
Frequently asked questions
Can a pinched nerve in your back cause knee pain?
Yes. Irritation of the L3 or L4 nerve roots commonly causes pain at the front or inside of the knee, and irritation of the L5 or S1 roots (classic sciatica) can cause pain behind or outside the knee and down the leg — even with a healthy knee.
Can sciatica cause pain behind the knee?
Yes. The sciatic nerve runs down the back of the thigh and divides just above the knee, so sciatica often produces pain, tingling, or tightness behind the knee, sometimes continuing into the calf.
How do I know if my knee pain is from my back or my knee?
Knee-origin pain usually changes with knee movement and loading, and the knee exam reproduces it. Back-origin pain often comes with burning, tingling, or numbness, travels from the buttock or thigh, changes with back positions like sitting or bending, and isn’t reproduced by examining the knee. A clinical assessment with nerve tension tests can usually tell the difference.
Can hip problems cause knee pain too?
Yes. Hip arthritis frequently refers pain to the knee — in one study nearly half of hip arthritis patients had pain below the knee. A thorough exam should always include the hip.
Will knee pain from sciatica go away?
Often, yes, once the irritated nerve settles. Many cases improve with conservative care — hands-on treatment, nerve mobility exercises, and strengthening. Seek urgent care for saddle numbness, bladder or bowel changes, or rapidly worsening weakness.
References
1. Kido T, et al. Clinical diagnosis of upper lumbar disc herniation: Pain and/or numbness distribution are more useful for appropriate level diagnosis. Journal of Orthopaedic Science. 2016;21(4):419-424. doi:10.1016/j.jos.2016.03.003
2. Khan AM, et al. Hip osteoarthritis: where is the pain? Annals of the Royal College of Surgeons of England. 2004;86(2):119-121. doi:10.1308/003588404322827518
3. Tamagawa S, et al. Impact of Severe Hip and Knee Osteoarthritis on Patient-Reported Outcomes and Global Alignment Following Lumbar Spinal Stenosis Surgery. Spine. 2025. doi:10.1097/BRS.0000000000005340
4. Bedson J, Croft PR. The discordance between clinical and radiographic knee osteoarthritis: a systematic search and summary of the literature. BMC Musculoskeletal Disorders. 2008;9:116. doi:10.1186/1471-2474-9-116
5. Santilli V, Beghi E, Finucci S. Chiropractic manipulation in the treatment of acute back pain and sciatica with disc protrusion: a randomized double-blind clinical trial of active and simulated spinal manipulations. The Spine Journal. 2006;6(2):131-137. doi:10.1016/j.spinee.2005.08.001
