What causes knee osteoarthritis pain?

Knee osteoarthritis is cartilage loss, bone remodeling, and synovial inflammation (inflamed joint lining) happening together. It is not a single tire wearing thin. Knee pain after an injury follows the same final path. It can follow a meniscus tear, an ACL injury, or a fracture that healed with the joint surfaces no longer lined up. Either way, the joint that hurts today is not the joint that was hurt years ago. It has been remodeling (reshaping) itself, badly, the whole time in between.

The mechanism, mechanical and metabolic

Two drivers do the damage. The first is plain load. Every pound of body weight turns into several pounds of force across the knee with each step. A joint already missing cartilage has no room left to absorb it. The second is metabolic, and patients are rarely told about it. Systemic inflammation from insulin resistance flows through the joint fluid itself. It speeds up cartilage breakdown no matter how much weight is on the knee. A thin patient with poor metabolic health can have aggressive osteoarthritis. A heavier patient with good insulin sensitivity sometimes does not. A third factor, behavior, closes the loop. A knee that hurts to move gets moved less. The muscles that steady it get weak, and weight goes up. That raises the load, which raises the pain. Breaking that loop, not just lowering today’s pain number, is the real goal.

Confirming the joint is the source

Knee pain is not always knee pain. Hip disease sends pain to the knee often enough that we examine the hip on every knee visit. A lumbar nerve root can also cause pain that patients feel at the front of the knee. An image-guided intra-articular injection confirms the joint itself is making the pain before we build a plan around treating it. Relief after the injection is diagnostic information, not just a treatment bonus.

What treats knee pain without surgery?

The load and metabolic terrain

Every procedure above buys the joint time and quiet. Whether that time holds depends on the load and the metabolic driver underneath it. That means targeted strengthening that protects the joint without feeding the pain cycle. It also means the same insulin-resistance work we build into every chronic pain plan, because a joint bathed in inflammatory signaling will keep breaking down cartilage no matter how well the nerve pain is controlled. See metabolic health and pain and sleep, movement and behavior for how that piece is built.

When is knee replacement the right answer?

Some knees are past what any of the above can offer. One is bone-on-bone with a fixed deformity. Another is a joint that fails an honest trial of the treatments above without lasting relief. In that patient, replacement is not a failure of conservative care. It is the correct next step. We say so directly rather than stack another injection onto a joint that has already told us what it needs. Where replacement is right, we work with your surgeon instead of competing with the referral.

Which knee symptoms are red flags?

• A hot, swollen knee with fever — needs same-day evaluation for a septic joint, not an osteoarthritis workup.
• The knee giving way or locking — suggests a mechanical problem, like a loose body or a torn meniscus fragment that injections will not fix.
• Sudden inability to bear weight after an injury — rule out a fracture before anything else. See when it is an emergency.

Orthobiologic treatment options

PRP is one of three orthobiologics we use in the knee. Bone marrow concentrate and microfragmented fat are the other two, chosen by how worn the joint is. Two things we control decide the result: the platelet dose that actually reaches the joint, and the rehab that follows. We prepare a high-dose product, place it under image guidance, and rebuild the thigh muscles that absorb every step. You stay awake under local anesthetic, and most people drive themselves home. Coverage is the plan’s budgeting call, not a verdict on the treatment, and HSA and FSA funds can generally be used.

If your X-ray already says bone on bone, start with bone-on-bone knee, which covers what is still possible at grade 4. If the pain starts higher up, read hip arthritis, because a worn hip often sends its pain to the knee.

Frequently asked questions

Can I book a knee pain visit without a referral?

Yes. You can schedule directly, with no referral and no prior imaging. A few insurance plans, mostly HMOs, still want a referral from your primary care doctor on file before they pay, so check your card or ask us to check it. Referrals, insurance and pain care explains how to tell which kind of plan you have.

How do I know if it’s the knee and not the hip or back?

Hip disease often sends pain to the front of the knee, and a lumbar nerve root can do the same. Both are covered in more detail in hip pain. An image-guided injection into the joint itself is the most reliable way to confirm the source.

Will genicular ablation delay a replacement I actually need?

No. It does not change the joint surface itself. It can be repeated or stopped at any point without affecting a future surgery option. It buys time and function while that choice is made, instead of forcing it too early. Radiofrequency ablation covers how the nerves regrow and what that means for repeat treatment.

Is PRP the same as a stem cell injection?

No. PRP concentrates your own platelets and their growth factors from a blood draw; it does not involve stem cells. We will explain exactly what is in the syringe before any orthobiologic procedure, not after. What to expect covers how we walk through options at the first visit.

Do I need to lose weight before you will treat me?

Weight is one input into the load driver, not a requirement for treatment. A knee that hurts too much to move makes weight loss harder, not easier. We treat the pain and the metabolic terrain together, at the same time, as covered in metabolic health and pain.

What kind of specialist should I see for knee pain?

Start with a physician who examines more than the knee. Hip disease and an irritated lumbar nerve root can both cause pain you feel at the knee, so we examine the hip at every knee visit and can confirm the joint with an image-guided injection. From there, the options run from joint injections to nerve treatment to PRP. If your knee needs a replacement, we coordinate with your surgeon.

Is there an injection instead of knee replacement?

For many knees, yes, there are real options before replacement. Image-guided corticosteroid or viscosupplement injections calm inflammation. Genicular nerve ablation quiets the nerves that carry knee pain. And PRP improved pain and function over placebo in a 2026 review of randomized trials. None of them rebuilds a bone-on-bone joint with a fixed deformity. For that knee, replacement is the correct next step, and we say so.

What should you not do with knee osteoarthritis?

Do not stop moving. A knee that hurts gets used less, the muscles that steady it weaken, weight goes up, and the extra load brings more pain. Targeted strengthening protects the joint without feeding that cycle. And do not accept “come back when it is bad enough for surgery” as a plan: the joint keeps remodeling while you wait, and inflammation from insulin resistance keeps wearing down cartilage.

Related reading

• Orthobiologics and PRP injections in St. Louis
• Genicular nerve block
• Radiofrequency ablation
• Image-guided joint injections
• Hip pain
• Metabolic health and pain
• Bone-on-bone knee
• Hip arthritis