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PRP Doesn’t Help Cartilage Repair? Always Read the Fine Print!

POSTED ON IN Latest News Regenexx-SCP BY Chris Centeno

prp cartilage repair

It’s always bizarre to me what makes the rounds of the science news. This week it was a paper, that websites covered, with the headline, “Platelet-rich plasma does not promote stem cell-mediated cartilage repair.” Like many research papers that are hyped, you always need to read the fine print. When you do, this headline isn’t accurate. Let me explain.

What Is PRP?

PRP is an acronym for platelet-rich plasma. It’s basically what you get when you concentrate the platelets in the blood. It’s used extensively throughout medicine, especially in orthopedics, to help with tissue repair. We have high-level research evidence that it can help tendon repair and strong evidence that it helps mild to moderate knee arthritis symptoms. There’s also strong evidence it helps low back pain caused by a painful lumbar disc.

What Prior Evidence Exists That PRP Helps Cartilage Repair

PRP has been extensively studied in the lab for cartilage repair. As one example, just last year, an animal study comparing two different types of PRP demonstrated that the amber PRP (the type we use, which is red- and white-blood-cell poor) was better at cartilage repair than red PRP. However, both helped cartilage repair (see images below from that study):

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Other studies follow:

Bizarrely, at the same time that the paper claiming PRP didn’t help cartilage repair was published, another paper was published in a different journal that concluded that it did help stem cells turn into cartilage. What was the difference? This paper actually used PRP; whereas, the hyped paper never actually used PRP. What? Let me explain.

Understanding Different Platelet Products

The people who wrote the crazy headlines seem to have no education on the different products that are made from platelets or how they work. Platelets help your body heal when there is an injury by doing two major things. The first is that they form a clot. This is critical in that it stops bleeding, and as the wound heals, the platelets cause the clot to contract to help to pull the two ends of the tissue damage together. The second is that the platelets release growth factors over seven days to stimulate healing and bring in cells that can do the repair job. This week-long growth-factor party is coordinated day by day to enhance healing, meaning more of some types of growth factors are released on day one versus more of others on day seven.

There are other things you can do with platelets in the lab. You can create what’s called a releasate, which is what the authors of the much-hyped paper did. To do this, you add a clotting agent to the PRP and let it form a clot. The platelets will release some of their growth factors due to the clotting agent. You then throw away the clotted platelets before they have a chance to release the rest of their growth-factor payload. So if PRP is a seven-day, carefully coordinated growth factor healing party, a releaste is an artificial mishmash of some of the growth factors from the platelets. Basically, the difference between Beethoven’s Ninth Symphony (PRP) and that random cacophony of sound you hear as a band or symphony warms up their instruments (releasate).

The Hyped Paper Never Used PRP in Its Experiments

The hyped research paper that found that “PRP” didn’t help stem cell-mediated cartilage repair in a lab study never used PRP. They used a releasate. Meaning, while the other paper published at the same time used the whole platelets to deliver Beethoven’s Ninth Symphony of carefully timed and controlled growth factors to coax tissue healing, the hyped one used the growth factor mishmash and threw away the platelets. So why does their title state that they used PRP? Who knows. However, the honest title would have been “Effect of Platelet-Rich Plasma Platelet Releasate on Chondrogenic Differentiation of Adipose- and Bone Marrow-Derived Mesenchymal Stem Cells”

Why One Paper Made the Science News and the Other Didn’t

You would think that science is blind and not at all impacted by business. However, a great example of the business of science is the publishing industry and how that impacts what doctors and patients believe. In this case, the publisher issued a press release on this paper, likely trying to get eyeballs on its journals, which in turn would drive paid research paper downloads and subscriptions. Those press releases then form the basis for news stories, which doctors and patients read. So unless they took the time to dig deeper, they now believe that PRP doesn’t help cartilage repair. However, that’s why you read this blog!

The upshot? There is ample evidence dating back at least to 2005 that PRP helps cartilage repair. It also helps stem cells differentiate into or repair cartilage. However, in the case of this hyped paper, the researchers never used PRP. Hence, always read the fine print or this blog!


    Barb says

    I had Regenexx do PRP injections for arthritis in my knee 4 months ago and had 80% improvement. Just had my other knee done last week. Hopeful to continue to remain active & eventually do stem cell injections for continued healing!


    Regenexx Team says

    Great to hear you're doing well! Being Proactive, like you are being, is a winning plan!


    Andy Pitas: Wendy Dickson. says

    PRP does work. I have had 5 treatments. My wife has had 2. We have recently been elected to the Huntsman World Senior Games Hall of Fame (track and field). In addition, I had demonstrable (x-ray) osteo-arthritis in my left knee. In 5 days it was gone and for the last 6 years it has not come back. Our work-out is what would be expected for top level track and field athletes. We are in our mid 70's. I have set 5 HWSG( and probably world) records since the PRP. I could barely hike and walk because of arthritis and no knee cartilage after years of major rock climbing and soccer and track and field. PRP fixed that , and helped my wife as well. Recently I had plasma-ozone (2) . Got 5-6 years from original PRP. If anyone thinks these procedures don't work I invite them to sprint and jump against me. I am 75 and am basically healed. I am encouraging my daughter (tennis elbow and back issues) to get these treatments, especially since she lives and works about 1 mile from your clinic. Surgery , especially in regard to power athletes (in our case) is the end of the line. A waste of time and money and your mobility as well.


    Regenexx Team says

    Thanks for sharing your story - great to hear you're doing so well! You may enjoy these like minded people: and and


    Adam says

    Has the effect of precisely injected PRP into the chondral lesion(s) site(s) been studied in contrasts to PRP injections into the articular space?

    Also, gotta love how Regenexx is shinning a bright light on otherwise suspicously dark nooks of medicine.


    Chris Centeno says

    Adam, there are a few surgical studies that try to localize the PRP, but that's comparing apples to oranges. So no injection localization studies vs. IA.


    Cristina says

    Dr Centeno, could you please give the citation of the two papers that you are referring to?
    I think there are many methods to separate platelets and there are few scientists who can obtain the maximum results with only “PRP”. But it is true that platelets stimulates SC to diferénciate into cartilage, as well other tissues too.
    Thank you!


    Regenexx Team says

    The links to the papers are in the blog. It all depends on whether there are enough stem cells to stimulate in the joint.


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    About the Author

    Chris Centeno

    Christopher J. Centeno, M.D. is an international expert and specialist in regenerative medicine and the clinical use of mesenchymal stem cells in orthopedics. He is board certified in physical medicine as well as rehabilitation and in pain management through The American Board of Physical Medicine and Rehabilitation.…

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