Being on the knee replacement waiting list does not always mean the knee is finished. One trial studied 90 people with bone-on-bone knee arthritis. All were already on that list, and in effect had been told they were out of options. Platelet-rich plasma (PRP) cut their pain, improved function, lowered opioid use and put off surgery for most of them.
Researchers randomized them anyway. Each got two platelet-rich plasma injections, a cortisone injection, or an anti-inflammatory tablet. Then the researchers watched what happened.
Nobody in the PRP group dropped out. Six people in the other two groups went on to have their knee replaced earlier than planned.
That is the finding to think about. It answers something no scan can tell you. Does being on the list mean your knee is finished? Or only that the standard steps ran out before anyone looked further?
Does PRP work for bone-on-bone knee arthritis?
The study is Lacko M and colleagues, Journal of Orthopaedic Surgery and Research, in press (accepted 26 May 2026). The patients had Kellgren–Lawrence grade 3–4 osteoarthritis. That is the advanced end, the stage where “bone on bone” gets said out loud.
In the PRP group, pain on the visual analogue scale fell from 6.2 to 3.3 and held at 3.7 at final follow-up. Function measured by WOMAC improved from 49.0 to 32.5. The need for opioids fell. Blood markers moved in step with all of that. COMP, MMP-3, IL-6, IL-18, TNF-α and CGRP went down. sTREM2, sRAGE and TGF-β1 went up.
The anti-inflammatory group did not just do worse. It went backwards — WOMAC worsened from 49.0 to 57.9. The people taking the tablet functioned worse at the end of the study than when they started.
A second trial, run by a different team, points the same way. Sánchez Santiuste and colleagues published in the Journal of Clinical Medicine in November 2025. They studied 86 patients with grade III–IV disease. Intraosseous PRGF (placed into the bone) beat intraosseous saline. Clinically important improvement was reached by 66.7% versus 46.3%.
Is PRP a cure or a bridge to knee replacement?
This is where this field often overreaches, so let us be exact.
Cartilage did not grow back. The authors make no such claim, and neither do we. Their own words for what PRP did here are “safe bridge therapy prior to arthroplasty.”
A bridge. Not a cure. Not regeneration. Not a permanent alternative to replacement.
What it means is narrower and more useful. In people with advanced arthritis who were already booked for surgery, a non-surgical injection gave real pain and function gains. It lowered opioid use. And it put off an operation for most of them.
What happens if I delay knee replacement?
A knee replacement cannot be undone.
If replacement is still the right answer for you in eighteen months, it will still be there in eighteen months. The reverse is not true. There is no way back to your own knee once it has been removed. That one-way door is the whole argument for doing things in careful order. It is rarely part of the conversation.
There is a second reason, for younger patients. Implants only last so long. Getting the first replacement earlier makes a second surgery to redo it (a revision) more likely later. And revision is a harder operation than the first. Delay is not merely avoidance — for some people it changes how many operations they will have in a lifetime.
The step that usually gets skipped
The standard path runs: anti-inflammatories, then physical therapy, then cortisone, then replacement. When the cortisone stops working, the path is used up and surgery is what is left.
But cortisone losing its effect does not prove the joint is beyond help. It tells you the driver of the inflammation was being muted, not addressed. And repeated cortisone has its own trial data on cartilage worth reading before the next one.
Nothing in that path asks why this joint is degrading faster than the other one. Insulin resistance, whole-body inflammation and poor blood flow to the tissue do not show on an X-ray. And they do not go away because a joint is replaced. A knee can be replaced in a body that is still wearing down the next joint.
What should I ask before scheduling a knee replacement?
Am I on this list because the knee cannot be saved, or because the standard steps ran out? Has anyone checked the metabolic and inflammatory drivers, or only the structure on the scan? What is my realistic result, not the average, but for someone my age, weight and metabolic health? If I wait six to twelve months and try a biological approach first, what exactly do I lose? And if I am not one of the people who does well, what are my options after that?
A surgeon who welcomes those questions is a good sign. One who treats them as an obstacle has told you something too.
Where we stand
We are not against knee replacement. It is the right operation for a great many people. For a knee that is truly finished, nothing else restores that function.
We are against taking the step you cannot undo before the ones you can undo have been honestly tried. That goes double now that there is randomized evidence, in exactly this group, that a real share of people get enough relief to wait.
If you are on a waiting list and nobody has looked past the X-ray, get a second opinion before the date arrives.
Frequently asked questions
Can anything be done if I am already on the knee replacement waiting list?
That is exactly the group this trial studied. Ninety patients with grade 3–4 osteoarthritis, all already booked for replacement, were randomized to PRP, cortisone or an anti-inflammatory. In the PRP group nobody dropped out. Six patients across the other two groups went on to earlier replacement. Being on the list is not the same as having no options left. But what applies to your knee takes an exam and evaluation.
For what can still be done for a bone-on-bone knee, read Bone on Bone Knee? Why “Nothing Can Be Done” Is a Lie.
Does PRP regrow cartilage?
No, and be skeptical of anyone who says otherwise. The trial authors call PRP here a “safe bridge therapy prior to arthroplasty.” It improved pain, function and opioid need, and it put off surgery. It did not rebuild the joint. The honest answer on cartilage regrowth is worth reading alongside this.
Is there a risk in waiting?
Replacement is still available later, and that is the main point. The operation cannot be undone. The delay can. For younger patients there is also a point in the other direction. Implants only last so long, so an earlier first replacement makes a later revision more likely. Talk this through with both your surgeon and a physician who checks the non-surgical options.
For how PRP works as a bridge to replacement rather than a substitute, read Advanced knee osteoarthritis: when PRP is a bridge, not a substitute.
Why did the anti-inflammatory group do worse?
In this trial, the aceclofenac group’s WOMAC score moved from 49.0 to 57.9. They were worse at the end than at the start. An anti-inflammatory mutes a signal without addressing what causes it. The long-term data on daily anti-inflammatory use is its own subject.
I have been told I am too young for a replacement. What does that mean?
It usually means the surgeon is weighing how long an implant lasts against how many years you have left. They would rather you have one operation later than two or three starting now. That window is exactly when the biological options are worth a look. We have written separately about not wasting it.
What can be done for a bone-on-bone knee without surgery?
One trial studied 90 people with grade 3–4, bone-on-bone knee arthritis who were already on the replacement list. Two platelet-rich plasma (PRP) injections lowered pain on the visual analogue scale from 6.2 to 3.3. They improved WOMAC function from 49.0 to 32.5. Opioid use fell, and surgery was put off for most of them. That is relief and time, not new cartilage.
What is the injection people try before a knee replacement?
In the waiting-list trial it was platelet-rich plasma: two PRP injections, compared against a cortisone injection and an anti-inflammatory tablet. The PRP group did best, and nobody in it dropped out. The trial authors call PRP a safe bridge therapy prior to arthroplasty. It buys time before surgery. It is not a lasting substitute for a knee that is truly finished.
Key takeaways
- Ninety patients with grade 3–4 knee osteoarthritis, all already on the replacement waiting list, were randomized to PRP, cortisone or an anti-inflammatory tablet.
- Nobody in the PRP group dropped out of the study. Six patients across the two other groups went on to replacement earlier than planned.
- The authors call PRP here a “safe bridge therapy prior to arthroplasty”: putting off surgery, not regrowing cartilage.
- The anti-inflammatory group went backwards. WOMAC worsened from 49.0 to 57.9, worse at the end than at the start.
- Replacement stays available later. The operation cannot be undone. The delay can.
This article is educational and is not a substitute for evaluation, diagnosis, or treatment by a physician. Individual results vary, and not every patient is a candidate for the therapies described. Do not start, stop, or change any treatment without consulting your physician.The Lacko trial is cited as in press.
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