What Is PRP Therapy and How Is It Used in Regenerative Medicine?

PRP, platelet-rich plasma, is your own blood spun down to concentrate the platelets and injected into a joint, tendon or injury. Whether it helps depends on three things: the condition, the preparation, and what it was compared with. Placebo-controlled trials were negative for knee arthritis and the Achilles tendon and showed little benefit for tennis elbow; against cortisone, PRP has done better in the mid term for several tendon problems; and orthopaedic and rheumatology sources still disagree about the knee.

What is PRP, and how is it made?

Blood is drawn from your arm. In OrthoInfo’s words, “The platelets are separated from other blood cells and their concentration is increased by spinning the blood down during a process called centrifugation” (OrthoInfo). The concentrate is then injected where you have pain. Platelets release growth factors, and the idea is that concentrating them supports healing. That is the rationale; whether it helps is a question for trials, below.

PRP contains platelets, not stem cells. It is a different product from bone marrow concentrate, although some clinics offer both; stem cell products follow different rules, set out in the overview of stem cell treatments and how they are regulated.

Is all PRP the same?

No. PRP can be made with more or fewer white blood cells left in. OrthoInfo describes “leukocyte rich PRP” and “leukocyte poor PRP” and says “the effectiveness of leukocyte rich PRP vs. leukocyte poor PRP … has not yet been determined” (OrthoInfo, above). The American Academy of Orthopaedic Surgeons’ 2021 overview of PRP for knee arthritis points to “the heterogeneity of the products and of the related study findings” and calls for studies “to evaluate the potential of each proposed PRP product” (<a href="https://www.aaos.org/globalassets/quality-and-practice-resources/biologics/technology-overviewprp-for-knee-oa.pdf”>AAOS technology overview, 2021).

That variation matters more than it might seem. A trial result describes one preparation, given on one schedule, to one group of patients. Before you apply it to the PRP a clinic offers you, it is worth knowing which kind the clinic makes, how many injections it plans, and whether any published trial used the same preparation for your condition.

What does the evidence show, condition by condition?

Condition	Compared with	What the best evidence cited here found	Source
Knee arthritis	Saline placebo	In a trial of 288 people, three PRP injections did no better than saline for pain at 12 months	University of Melbourne, on the RESTORE trial
Knee and hip arthritis	Guideline review	The American College of Rheumatology recommends against PRP	ACR
Tennis elbow (lateral elbow pain)	Placebo	32 trials, 2,337 people: pain 0.16 points better on a 10-point scale at three months, moderate certainty; the reviewers concluded the data "do not support the use of autologous blood or PRP injection"	Cochrane, 2021
Achilles tendinopathy	Sham needle	One PRP injection did no better at six months	Kearney, JAMA 2021
Rotator cuff problems, tennis elbow, plantar fasciitis, tenosynovitis	Cortisone	Better than cortisone in the mid term in a review of 27 trials, with unclear blinding in most	BMC Musculoskeletal Disorders, 2025
Added during rotator cuff or ACL surgery	Surgery without PRP	OrthoInfo: "the results so far show little or no benefit"	OrthoInfo, above
Fractures	Standard care	OrthoInfo: "it has shown no significant benefit"	OrthoInfo, above
Chronic diabetic wounds	Coverage decision	Medicare covers PRP for chronic non-healing diabetic wounds, a use outside the joints	CMS, NCD 270.3

Sources for the table: University of Melbourne, on the RESTORE trial; ACR; <a href="https://www.cochrane.org/CD010951/MUSKELautologous-blood-or-prp-injection-lateral-elbow-pain”>Cochrane, 2021; Kearney, JAMA 2021; BMC Musculoskeletal Disorders, 2025; CMS, NCD 270.3.

Each row answers a narrower question than it may look. A result in tennis elbow tells you little about a knee, and a result against cortisone tells you little about how PRP compares with doing nothing. The useful move is to find the row closest to your own condition, then read its second column before its third.

Why do major sources disagree about PRP for the knee?

The American Academy of Orthopaedic Surgeons’ 2021 technology overview concluded that “PRP may have more benefit than placebo for improvement of pain and patient reported outcomes related to symptoms, for time points up to one year after injection,” while adding that “whether PRP can improve the structure or functioning of the osteoarthritic joint remains unclear” (AAOS technology overview, above). The American College of Rheumatology recommends against PRP for knee and hip arthritis (ACR, above), and the largest single placebo-controlled trial, RESTORE, found no difference from saline at 12 months after three weekly injections of one leukocyte-poor preparation (JAMA).

Five differences in method help explain the split:

Dates. The ACR guideline was published in 2019 and the AAOS overview is dated August 2021. RESTORE was published in November 2021, so neither document could weigh it.
Kind of document. The ACR document is a treatment guideline that issues recommendations. The AAOS document is a technology overview that summarizes studies and “does not make recommendations for or against the use of platelet rich plasma.”
Products. Preparations differ in white cell content and schedule. A negative trial of one does not rule out another, and a positive pooled result may mix products that do not all work.
Comparators. In the sources on this page, PRP looked better against cortisone, whose relief is expected to fade, and weaker against a saline placebo, which is the test of whether PRP itself does anything.
Many small trials versus one large one. Pooling small studies can show a modest average benefit that a single large, well-controlled trial does not reproduce.

What would settle it is large placebo-controlled trials of specific, standardized preparations, close to what the AAOS overview calls for. Whoever recommends PRP for your knee, or advises against it, should be able to say which preparation and which trials the advice rests on.

Risks and warning signs

PRP is an injection, so the risks of any injection apply, including infection. OrthoInfo describes its risks as minimal (OrthoInfo, above), but being made from your own blood does not remove the risk of germs entering a joint. The signs that need a prompt call, and what to do about blood thinners and other medicines before and after, are the same as for other injections and are listed on the page about the days after a procedure. Do not stop a prescribed blood thinner or aspirin without the doctor who prescribed it.

What should a PRP recommendation be able to explain?

It should name your condition and the preparation the clinic uses, point to a trial in that condition, say what the trial compared PRP with, give the number of injections and the total cost, and describe how you and the clinician will judge whether it worked before you consider a second injection. If the plan after a non-response is a pricier injection, the reason for that step should be as clear as the reason for the first. A question list for a first appointment turns these into things to ask in the room, and the warning signs that a clinic is overselling results apply to PRP as much as to stem cells.

What makes the case for PRP stronger or weaker?

This is a question about how much evidence supports considering PRP, not a prediction that it will work for you. That evidence is stronger for conditions where PRP has done better than cortisone in the mid term than for conditions where placebo-controlled trials were negative, and it is more relevant when the clinic’s preparation matches one used in a trial for your condition. Your situation can add reasons to consider it: you have done a proper exercise program and still have pain, or you want to avoid repeated steroid shots. It uses your own blood, and its listed risks are those of an injection. The evidence is weaker where placebo-controlled trials found a small difference or none, as in the largest knee trial, the Achilles and the elbow, and the cost weighs more when the plan runs to several injections or joints at cash price.

The same choice lands differently by condition. Someone with plantar fasciitis who has done the stretching and still has heel pain, and is weighing a second steroid shot against PRP, is in the row where PRP has done better than cortisone in the mid term. Someone with knee arthritis weighing the same two shots is in the contested row, and the trial that tested PRP against saline is the one that speaks most directly to whether PRP itself helps.

Where PRP stands for your condition

For knee or hip arthritis, it is contested: the rheumatology guideline and the largest trial point one way, the orthopaedic overview another. For tennis elbow and the Achilles tendon, the placebo-controlled evidence does not support it. For other tendon problems it has beaten cortisone in the mid term, which is a real but lower bar than beating a placebo. If you choose it, knowing which of these you are in, and agreeing in advance how you will judge the result, matters more than any single study.

This page is general information, not medical advice.

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