The short answer
Yes — for the right knee, at the right stage
Platelet-rich plasma has more published evidence behind it for knee osteoarthritis than for any other use, and the weight of that evidence is positive. Multiple systematic reviews and meta-analyses find PRP improving pain and function compared with placebo, with the clearest and most consistent effects in the three-to-six-month window after treatment.
Talk to a physiatrist about your kneeWhat it is
Concentrating your own repair signals
We draw a small amount of your blood, spin it in a centrifuge to separate out the platelet fraction, and inject that concentrate into the joint. Platelets carry growth factors — the signalling proteins your body already uses to repair tissue. Nothing synthetic is added.
That autologous quality is why PRP carries essentially no allergy risk and why it is permitted under current anti-doping rules, which matters to competitive athletes considering their options.
The evidence
What the studies actually found
Reading the literature honestly means acknowledging that it is not unanimous. Here is the shape of it:
- Compared with placebo, meta-analyses generally show significant improvement in both pain and function — most reliably at three and six months.
- Results at twelve months are inconsistent. Some analyses show benefit persisting; others find the difference has narrowed or gone.
- Leukocyte-poor PRP — a preparation with fewer white cells — outperforms leukocyte-rich preparations in most comparisons for knee osteoarthritis.
- Benefit is clearest in mild-to-moderate disease. Advanced osteoarthritis responds considerably less well.
- At least one umbrella review concludes the effect size up to six months is real but modest, and debates whether it is clinically meaningful for every patient.
That last point deserves saying out loud. PRP is not a miracle, and a clinic that presents it as one is not reading the same papers.
Comparison
PRP versus the alternatives
| Option | Typical effect | Main drawback |
|---|---|---|
| Corticosteroid | Fast, strong short-term relief | Wears off in weeks to months; repeated use is associated with cartilage and tendon deterioration |
| Hyaluronic acid | Modest, gradual | Head-to-head analyses generally favour PRP in mild-to-moderate disease |
| PRP | Gradual onset, benefit strongest at 3–6 months | Costs more; not covered by insurance; does not rebuild cartilage |
| Knee replacement | Definitive for advanced disease | Major surgery; reserved for severe arthritis |
Good candidates
Who tends to do well
- Mild-to-moderate osteoarthritis on imaging, not bone-on-bone
- Pain that has not settled with physical therapy and load management
- People who want to delay or avoid joint replacement
- Patients who have had cortisone before and do not want to keep repeating it
- Active adults whose symptoms limit activity rather than daily function entirely
Poor candidates
When we will tell you not to bother
Part of the value of seeing a physiatrist rather than an injection service is being told when the answer is no.
- End-stage, bone-on-bone arthritis — a surgical opinion is usually more useful
- Knee pain that is actually coming from the hip or lower back, which an examination can distinguish
- Mechanical symptoms — true locking or giving way — that point to a structural problem
- Active infection, or certain blood and platelet disorders
Practicalities
What a course of treatment looks like
Examination and imaging review
Establish what is generating the pain and how advanced the arthritis actually is. This determines whether PRP is sensible at all.
Draw and preparation
Blood is drawn in the office and centrifuged while you wait.
Injection
The concentrate is injected into the joint, with guidance where accuracy matters. Local anaesthetic is used.
The next few days
Expect increased soreness for several days. That inflammatory response is part of the mechanism, not a sign of failure.
Rehabilitation
Loading and strength work in the following weeks. Anti-inflammatories are usually paused around treatment because they blunt the signalling PRP relies on.
Review
Assess response before deciding whether further injections are worthwhile. A series is common.
FAQ
Frequently Asked Questions
How long does PRP last in the knee?
The published benefit is clearest through three to six months. Some patients report longer, and twelve-month data varies between studies. Many people plan for repeat treatment rather than expecting one injection to be permanent.
How many injections will I need?
A series is common for knee osteoarthritis rather than a single treatment. The number depends on your response, and you should be told the expected schedule before you start rather than discovering it as you go.
Is PRP better than a cortisone shot?
For short-term relief, cortisone often works faster. For chronic problems where you would otherwise be repeating steroid injections, PRP avoids the tissue-thinning concern associated with repeated corticosteroid. In mild-to-moderate knee osteoarthritis, comparative analyses generally favour PRP over both cortisone and hyaluronic acid at the three-to-six-month mark.
Does it hurt?
There is discomfort during the injection and typically several days of increased ache afterwards. Local anaesthetic is used, and most patients drive themselves home.
Is PRP covered by insurance?
Generally not. PRP is usually a self-pay treatment, which is another reason to be clear about whether you are a good candidate before starting.
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