Platelets are not just for clotting.

PLATELET-RICH PLASMA, EXPLAINED

Platelet-rich plasma [PRP, a concentrate made from your own blood] is autologous: it comes from you and goes back into you on the same visit. There is no donor material and no drug.

The procedure, start to finish

• Blood draw. A standard venous draw, the volume depending on the target.
• Centrifugation. The sample is spun to separate red cells from plasma and concentrate the platelet fraction.
• Preparation. The concentrate is drawn off. Platelet concentration, leukocyte content and volume are chosen for the tissue being treated — a tendon and an arthritic joint do not want the same preparation.
• Image-guided placement. Ultrasound or fluoroscopic guidance puts the injectate where it is meant to go. This is the step that separates a targeted injection from a hopeful one.
• Load management afterward. What you do in the following six weeks materially affects the result.

What the platelets are doing

Platelets are not only clotting cells. Their alpha granules carry PDGF, TGF-β, VEGF, EGF and IGF-1 — signals that recruit local progenitor cells, drive angiogenesis and influence how collagen is laid down and organized. In a healthy acute injury this cascade runs on its own and resolves. In a chronic one it has usually stalled.

Why a repair stalls in the first place

Three things commonly hold it there, and only one of them is mechanical.

• Metabolic inflammation. Chronic low-grade inflammatory signaling — NF-κB-driven, sustained by adipose tissue and hepatic crosstalk — keeps tissue in a degradative rather than a rebuilding state.
• Insulin resistance and hyperinsulinemia. These impair microvascular delivery and degrade collagen quality directly. A tendon in an insulin-resistant patient is repairing with poorer raw material.
• Load, economics and sleep. The tissue is re-injured before it consolidates — usually because the person cannot stop doing the thing that hurts it. Fragmented sleep compounds it: most tissue repair signaling is nocturnal.

This is why we look at your metabolic panel before treating a tendon. It is not upselling. It is the difference between recruiting a repair process and asking one to run in conditions where it has already failed once.

How many treatments, and how long

Most tendon and joint protocols involve one to three injections spaced several weeks apart. Response is gradual — this is a biological process, not an anesthetic, and people who expect same-day relief are usually disappointed at two weeks and satisfied at three months. Some people do not respond at all, and we say here than after you have paid for a series.

What the visit and recovery look like →

Not all PRP is the same preparation

The most consequential of those differences is the white cell concentration, which decides whether a preparation provokes inflammation or avoids it — and therefore whether it belongs in a joint or on a tendon. That decision is set out in full on leukocyte-rich and leukocyte-poor PRP.

This is the least understood fact about the treatment and it explains much of the inconsistency in the published literature. “PRP” names a category, not a product, and two clinics can deliver preparations that differ several-fold.

• Platelet concentration. Systems vary widely in how much they concentrate above baseline. More is not automatically better — there is evidence of a ceiling above which additional platelets add nothing.
• Leukocyte content. Leukocyte-rich preparations bring white cells and additional inflammatory signaling. In a tendon that may be useful. Inside a joint it is more contentious, and leukocyte-poor preparations are generally preferred intra-articularly.
• Red cell contamination. Residual red cells release free hemoglobin and iron into the target, which is pro-oxidant and counterproductive.
• Activation. Some protocols activate the platelets before injection; others rely on activation by collagen in the tissue itself. This changes how quickly the growth factors are released.
• Volume. What suits a knee joint is not what suits a plantar fascia.

A clinic using one protocol for every patient and every tissue has chosen convenience. When you read that trials of PRP are inconsistent, this is a large part of why: they were not testing the same intervention.

Why image guidance is not optional

A preparation placed next to the target rather than in it does nothing. Studies of blind injection accuracy are humbling across most sites — a knee without an effusion, a subacromial space, a hip joint, a specific degenerate segment of tendon are all missed at rates that would surprise most patients.

Ultrasound also does something guidance is rarely credited for: it lets us see what we are treating before we treat it. A tendon that looks intact, a partial tear nobody suspected, a bursa doing more than the tendon — each changes the plan in the room rather than three months later.

What we do at the same visit

An injection is the smallest part of the appointment. What surrounds it is an examination that includes the joints above and below, a review of imaging against that examination rather than in place of it, and a look at the metabolic picture that determines what raw material the repair will run on.

That last piece is the practice’s actual position rather than an add-on: tendon and cartilage repair are anabolic processes, and they proceed on the substrate available. Asking a tendon to rebuild in an insulin-resistant, chronically inflamed, sleep-deprived body is asking it to do the thing it already failed to do once.

What it will not do

• It does not regrow cartilage in an arthritic joint.
• It does not repair a large retracted tendon tear.
• It does not work quickly, and anyone who promises relief next week is describing a different mechanism.
• It does not work for everyone, and the honest figure is that a meaningful minority get nothing.
• It does not remove the need for the loading program, which does much of the work.

Related reading

• Platelet lysate — when platelets are the problem
• Why the trials disagree
• What we treat
• Am I a candidate?
• Recovery timeline
• Risks and side effects

A short history, and why it matters to you

PRP was not invented for orthopedics. It came out of transfusion medicine and was used in cardiac surgery and oral and maxillofacial surgery from the 1980s onward, where surgeons were looking for a way to improve graft and wound healing. Its migration into musculoskeletal medicine came later, accelerated considerably by professional athletes using it and by the coverage that followed.

That history explains two things. It explains the strong safety record — autologous blood products have been given to people for a long time. And it explains the marketing problem: a treatment popularized by athletes attracts claims that outrun the evidence, because the population it was publicized in is young, healthy, extremely well rehabilitated, and nothing like the average patient.

Reading a PRP study without being misled

If you are researching this yourself, four questions separate a useful study from a misleading one.

• What was the control? Against no treatment, almost anything looks good. Against an injected control, the comparison means something.
• How long was follow-up? Stopping at eight weeks favors corticosteroid; running to a year usually reverses the result.
• Was the preparation characterized? Platelet concentration and leukocyte content reported, or assumed? Most trials do not report them.
• Who was excluded? This is the one nobody checks, and it is the reason trial results may not describe you at all.

That last question is the subject of why your insurer will not pay for this, and it is the most useful thing on this website to understand before deciding anything.

What a realistic expectation looks like

Not a cure, and not nothing. For a well-selected patient with a degenerate tendon, a reasonable expectation is meaningful improvement in what the tissue tolerates, arriving gradually between six weeks and three months and continuing to consolidate for months after that.

For an arthritic joint, a reasonable expectation is a period of reduced pain and better function — commonly six to twelve months — in a joint whose imaging has not changed. Repeat treatment is normal rather than a sign of failure.

And for a minority of people in both groups, nothing. That figure belongs in the conversation before treatment, not after.

What people ask before their first injection

Is PRP a stem cell treatment?

No. PRP contains concentrated platelets and the growth factors they carry — no stem cells at all. Any clinic describing it as stem cell therapy is misdescribing what is in the syringe. What that phrase actually covers.

Does it hurt?

The draw is an ordinary blood draw and local anesthetic is used at the skin. Discomfort varies sharply by site — a knee joint is straightforward, a plantar fascia is among the more uncomfortable injections in musculoskeletal medicine and is done under a regional block. What the visit involves.

Why do I have to stop anti-inflammatories?

Because they suppress exactly the inflammatory signaling the injection was given to provoke. The window is agreed with you rather than applied as a blanket rule. Why the early phase matters.

How many injections will I need?

Commonly one to three depending on the tissue and the response, spaced several weeks apart. Partial response at three months is the clearest reason for a second. The assessment points.

Will it regrow my cartilage?

No. Nothing available today reliably does, and a treatment sold on that promise is overselling. What PRP appears to do in a joint is change the environment rather than the structure. What that means for an arthritic knee.

Is one clinic’s PRP the same as another’s?

No, and this is the least understood thing about it — platelet concentration, leukocyte content and volume all vary, and they should be chosen for the tissue being treated. Questions worth asking any clinic.

Is it covered by insurance?

Generally not. Medicare and the commercial payers decline to cover it, which is why this is a self-pay practice. What that classification is actually deciding.

What the injection is actually competing with

A repair is an anabolic process, and anabolism runs on what the body can supply. That makes the useful question not “does PRP work” but “what is it working against.”

In a metabolically healthy person it is working with the tissue. In someone carrying metainflammation it is working against a standing headwind: insulin resistance degrading microvascular delivery to an enthesis that was already the worst-perfused thing in the limb, glycation cross-linking the new collagen into something stiffer and more brittle than what it replaced, and a circulating inflammatory signal holding the whole environment in a demolition posture rather than a construction one.

You can deliver a perfect growth-factor signal into that and get very little. Not because the treatment failed, but because it was asked to build without materials.

Which is why we ask about things that sound unrelated

Your fasting glucose. Your sleep. Whether the job lets you offload the limb. Whether you live alone.

None of that is a preamble to selling you something and none of it is wellness advice. Each one is an input to the same equation, and a clinic that treats the tendon while ignoring them is doing precise work on a small part of the problem — which is the definition of a symptom-based silo and the reason so many people arrive here having already had competent care that did not help.

Where this actually sits with the FDA

Patients ask whether this is experimental, usually because of the wording in a denial letter. It is not. Whether a plan pays for something, and what that something is, are two separate questions.

• It is approved by the FDA for use in humans. The preparation systems are regulated medical devices with FDA clearance, and platelet-rich plasma is administered under that framework. This is established medical practice, not a trial and not an experiment.
• The material is your own blood. Drawn from you, concentrated, returned to you in the same visit. There is no donor material and no drug.
• You are not enrolled in anything. No study, no placebo arm, no protocol. A physician assesses you and treats you.

So why will my plan not pay for it?

Because the language in that letter is coverage language, not regulatory language. It means the plan has decided it will not carry the cost of this across its whole membership. It is a budgeting determination about what a plan buys.

It is not a statement that the procedure is unlawful, unproven for you, or experimental in the regulatory sense. Plans decline to cover plenty of lawful, well-established care, and they cover some things with weaker evidence than this.

The practical consequence for you is simple: this is a self-pay practice. We do not bill insurance, and you will know the cost before anything is drawn. What that means for you, including pre-tax accounts.