PRP Injections: What the Evidence Shows

Platelet rich plasma, or PRP, starts with a tube of your own blood. It is spun in a centrifuge so the platelets concentrate into a small volume, and that volume is injected into a joint or a tendon. Platelets carry growth factors the body uses to start repair, and the idea is to deliver a large dose of them exactly where healing has stalled. The idea is reasonable. The evidence depends entirely on where the needle goes.

Where the data is decent

• Knee osteoarthritis. The best studied use. In trials PRP has done modestly better than hyaluronic acid or saline for pain and function at 6 to 12 months in mild to moderate arthritis. One of the largest and most carefully run trials found no difference from saline at a year, so the picture is mixed but leans positive. It does not regrow cartilage. The honest summary is a modest, temporary reduction in pain for some people.
• Tennis elbow. Compared with a steroid injection, PRP tends to do worse in the first few weeks and better by 6 to 12 months, because steroids calm pain quickly but do nothing for the tendon.
• Plantar fasciitis. Smaller trials, mostly favorable when compared with a steroid injection. Patellar tendon trials are mixed.
• Hair loss. For pattern hair loss, small trials show increased hair density over several months.

Where the data is thin

Achilles tendinopathy trials have mostly been negative. Hamstring strains, the same. Rotator cuff and hip arthritis are inconsistent. Spine injections have little controlled data. Injections marketed for sexual function or cosmetic results have almost none. Those uses carry little risk beyond the injection itself, since it is your own blood, but they are being sold on the strength of the knee data.

Part of the problem is that PRP is not one thing. Platelet concentration, the presence or absence of white cells, the spin method and the number of injections all vary between clinics and between studies.

What to ask before paying

Expect to pay several hundred to a couple of thousand dollars per injection, out of pocket, since insurance rarely covers it. Before that, ask a few things.

• What is the diagnosis, and was it confirmed on imaging?
• Which preparation is used, and is it guided by ultrasound so it lands in the tendon?
• How many injections, and what happens if the first does nothing?
• What is the loading program afterward? A tendon heals under gradual load. An injection without a rehab plan is half a treatment.
• Will anti inflammatory pain relievers be held around the procedure? They blunt platelet function, so the physician doing the injection usually asks for a pause of a week or two, and that decision is theirs to make, especially for anyone on a daily aspirin.

A sore knee or a stubborn tendon is often the one thing keeping a 50 year old from training. If that is where you are, it's worth a conversation about the whole plan before the money goes in.

This article is educational and is not medical advice.

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