🥇 The Athlete Development Journal

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“What is PRP and does PRP work?”

The story.

Hines Ward was known for his infectious smile and killer instinct. He would lower his shoulder, nearly put a defender into a coma, and beam his pearly whites the whole time.

He was an insanely tough dude who loved the game.

In the 2009 AFC Championship game, however, Hines suffered an injury that even he couldn’t tough out. He had to come out of the game in the 1st quarter with an MCL injury.

Just two weeks later, he made a big splash by coming back and playing an important role in the Super Bowl.

He attributed his rapid return to a new(ish) treatment he received called platelet-rich plasma injections, or PRP for short.

The New York Times grabbed hold of that, ran an article, and thrust PRP into the mainstream spotlight.

Its use cases have evolved over the years. Professional pitchers inject it to heal partially torn UCLs, recreational adult athletes inject it to heal their arthritic knees, and Kim Kardashian injects it all over her face to get rid of wrinkles (seriously, it’s called a Vampire facial).

Today, it remains a hot topic. Many patients and physicians swear by it, but insurance companies don’t believe enough in its efficacy to pay for the treatment. So, let’s find out… what does the science say?

The science.

Our 2 main questions today are:

1. Is PRP effective at improving pain and function?
2. Is PRP safe?

Before we answer those, we need to establish some background knowledge.

The background: What’s the physiology?

There are 4 main ingredients of your blood:

1. Plasma: 55%
2. Red blood cells (aka erythrocytes): 44%
3. White blood cells (aka leukocytes): <1%
4. Platelets (aka thrombocytes): <1%

Platelets are crucial at jump-starting your body’s internal repair system, but they make up <1% of your total blood volume. So, the goal of PRP is to try to reconfigure the proportions of your blood ingredients to dose in a boat-load of platelets.

Here’s the process:

• Someone takes a blood draw from you.
• That blood is spun in a centrifuge. The fast rotation of the centrifuge separates your blood ingredients into different layers, because they have different weights.
  • White blood cells and platelets have similar densities, so you have to use a double spin method if you want to separate those.
• The platelets and plasma (and sometimes the white blood cells) are re-combined and injected back into your injured area.

Once the injection happens, the platelets are activated and release specialized proteins called growth factors that jump-start healing. There are over 30 bioactive proteins in platelets, but the big five are:

1. Platelet-Derived Growth Factor (PDGF): “The Project Manager”
   • recruits other cells to the area and tells them to start multiplying.
2. Transforming Growth Factor (TGF-β ): “The Mason”
   • builds the “scaffolding.” It stimulates the production of collagen and helps create the matrix for new bone and cartilage to grow on.
3. Vascular Endothelial Growth Factor (VEGF ): “The Electrician/Plumber”
   • creates new blood vessels (angiogenesis) to bring in oxygen and nutrients.
4. Epidermal Growth Factor (EGF): “The Finisher”
   • speeds up the growth of skin cells and helps wounds close up and heal from the outside in.
5. Insulin-Like Growth Factor (IGF-1): “The General Contractor”
   • works in almost every type of tissue in the body to ensure the local cells are healthy enough to handle the rapid repair process.

PRP is part of a category called orthobiologics: the use of naturally occurring biological substances to help injuries of the bones, joints, muscles, and tendons heal faster and more effectively.

It sounds great, right? Using your own body’s natural biological material to heal yourself sure sounds like a win to me.

That theory’s cool and all, but does it work?

Remember, our 2 main questions today are:

1. Is PRP effective at improving pain and function?
2. Is PRP safe?

To answer these 2 questions, I have 4 studies for us to work through. Then, at the end, we’ll form a cohesive narrative and I’ll give my current stance.

If you don’t care too much about the nitty gritty details and just want the answer, you can scroll down to the “The takeaways” section.

Let’s dive into our first study:

1) Systematic Review of Platelet-Rich Plasma for Low Back Pain. (Machado et al., 2023)

1. This was the beefiest systematic review on PRP for low back pain that I could find, consisting of 13 RCTs, 27 case series studies.
2. However, something about this study just rubs me the wrong way. They don’t report significance values for the individual studies, which I find very odd. They don’t report effect sizes or anything of the like. It just feels like they’re hiding some stuff.
3. Most of the studies were on intradiscal PRP injectiona and found significantly greater improvements in pain, function, and satisfaction than placebo. The improvements were maintained for “many years after treatment.”
4. Similar improvements were found for both epidural injections and facet injections.
5. It seems that higher platelet concentrations were associated with higher initial pain, but led to larger improvements in pain, function, and satisfaction in the long run.
6. Interestingly, there was evidence to suggest that platelet-rich fibrin (PRF) is maybe more effective for discogenic low back pain than PRP.
7. In all the studies, there were no complications such as progressive disc herniation or neurological deficits. Disc space infection was reported in only one study.
8. The preparation and types of PRP used were so diverse and all over the place.
9. There’s a surprising dearth of data.
   • “The use of platelet concentrates in surgical practice was first reported in the late 1990s, while the use of PRP for spinal pathologies has been described for over a decade. However, in more than 10 years, only 13 RCTs with limited patient samples and a few dozen case series have been conducted, predominantly derived from the authors’ clinical practices.”

My takeaway from this study:

• PRP is quite promising for LBP, but the statistical significance for individuals not being shown is a yellow flag.
• Furthermore, it appears really important to make sure the preparation of the PRP is appropriate and we should investigate PRF further.

This study was a good starting point, but I’d still like to know more about what the research says about PRP and low back pain. Cue the next study!

2) Platelet-Rich Plasma Treatment for the Lumbar Spine: A Review and Discussion of Existing Gaps. (Yum et al., 2024)

1. This is a high quality narrative review. A narrative review doesn’t have a pre-planned, systemized search strategy. So, it’s not reproducible like a systematic review is and it’s subject to more bias. However, this narrative review is thorough and descriptive. It does its job.
2. A couple of single-arm trials (which means there’s no control group) found some positive results. But, those studies must be taken with a strong asterisk. There’s no control group, so how can we know if that 14% “success” at 1 month to 47% “success” at 6 months was due to the PRP injection or just the natural healing power of time?
3. That’s where RCTs come in. The RCTs showed mixed results. Some found statistically significant improvements, some showed no difference, some showed improvements that weren’t statistically significant.
4. All of the RCTs had small sample sizes.
5. A facet-joint injection RCT that found corticosteroid injections were more effective at 1 month, but PRP was more effective at the 3 and 6 month marks. This again suggests that PRP might be something that works better over time.
6. Importantly, a couple of studies in different categories showed that higher concentrations outperformed lower concentrations.

My takeaway from this study:

• PRP seems to be effective over time, more effective with higher concentrations, and is in need of standardization of preparation and evaluation.

I feel like I have a good handle on what the evidence says about PRP and low back pain, but what about other areas of the body? Cue the next study…

3) Platelet‑rich plasma injection in the treatment of patellar tendinopathy: a systematic review and meta‑analysis. (Barman et al., 2022)

1. This is a solid systematic review.
2. PRP for patellar tendinopathy did not have significantly better results than non-PRP injection, saline injection, dry needling, stem cells injection, hyaluronic acid injection, high volume injection, or no injection.
3. The only thing it out-performed was extra-corporeal shock wave therapy.
4. Importantly, though, there were no safety issues, outside of temporary increased localized pain.
5. Also, importantly, this study doesn’t segment out and analyze the different categories of PRP.
6. I’ve got some concerns here. This study is supposed to be strictly about patellar tendinopathy. The world’s leading tendon researchers tell us that patellar tendinopathy is an issue that is often misdiagnosed. People get diagnosed with patellar tendinopathy, but it’s actually something else. Their rule is that if you’re not an explosive, young, jumping athlete, it’s most likely not patellar tendinopathy. The average ages in this study are awfully old for true patellar tendinopathy. So, there might be some issues here.

My takeaway from this study:

• PRP, as a general entity, might be unhelpful for patellar tendinopathy. However, this study does not parse out different subtypes of PRP at all.

Okay, every study is alluding to the same thing… all of these PRP injection factors are different. As one of the studies that I read, but didn’t make the cut to be reviewed in this entry so eloquently said:

“Standardization of those factors is essential to maximizing its clinical blessings.”

Let’s see what the evidence says about PRP factors. Cue up the next study!

4) Re-Evaluating Platelet-Rich Plasma Dosing Strategies in Sports Medicine: The Role of the “10 Billion Platelet Dose” in Optimizing Therapeutic Outcomes— A Narrative Review. (Corsini et al., 2025)

1. This is again a high quality narrative review. It does its job.
2. A systematic review by Berrigan et al. analyzed 29 RCTs and found 90% of studies with doses >5.5 billion platelets reported significant clinical improvements, while studies with ≤2.3 billion platelets failed to demonstrate therapeutic benefits (p < 0.01).
3. The review identified an ideal cumulative dose of 10 billion platelets across multiple injections for optimal efficacy. This suggests clinicians should aim for a minimum dose of 4 billion platelets per injection and a cumulative dose of 10 billion platelets across multiple treatments
4. Rotator cuff tendinopathy, lateral epicondylitis, gluteal tendinopathy, achilles tendinopathy, and plantar fasciitis all found that positive benefits with PRP, especially with platelet counts between 5-10 billion.
5. New data suggests that Leukocyte Poor-PRP (LP-PRP) may provide more pain relief than Leukocyte Rich-PRP (LR-PRP). Leukocytes can increase inflammation, which can negate some of the benefits of PRP.
6. However, not all leukocytes function similarly.
   • Neutrophils are highly inflammatory and may promote pro-inflammatory and catabolic effects, potentially detrimental to tissue healing.
   • Monocytes/macrophages, on the other hand, may promote pro-reparative properties and play a key role in tissue regeneration.
7. There is a consensus that RBC contamination should be minimized. Unlike platelets and leukocytes, RBCs do not contribute to tissue regeneration and may be detrimental to musculoskeletal tissues
8. Endogenously activated PRP seems to perform better than exogenously activated PRP.

My takeaway from this study:

• All PRP is not created equal.

The takeaways.

What’s actually important here?

1. We have some reason to believe that PRP is more effective at reducing pain and improving function than placebo or cortisone.
2. We have little to no reason to believe that PRP is unsafe.
3. We have strong reason to believe that all PRP is not created equally.

My stance: “Is PRP a safe and effective treatment?”

If someone:

• has rigorously modified their workload with a skilled PT,
• has gone through a prolonged exercise and manual therapy rehab program with a skilled PT,
• and still has not had relief from their pain,

then PRP is worth a shot.

The current evidence suggests that the type of PRP that is most effective has the following characteristics:

• a high platelet dose of 5 to 10 billion platelets per injection,
• a high cumulative dose of > 10 billion platelets over multiple injections,
• leukocyte poor PRP to reduce inflammation and tissue degeneration,
• minimal red blood cell contamination,
• and endogenous activation.

The Attia categories

To give clarity about how strong the current evidence is, I use these five categories to grade the interventions we discuss:

• Proven: Interventions supported by robust, reproducible human data where the probability of them being ineffective is near zero (creatine, whey protein, strength training, etc.).
• Promising: Treatments backed by strong mechanistic logic, animal data, or early human data that look effective but lack definitive long-term human trials.
• Fuzzy: Topics where the data is inconsistent, contradictory, or confusing, making it currently impossible to determine clear benefit or harm.
• Noise: Hyped interventions where the signal is too weak to form a conclusion because the “evidence” relies mostly on anecdotes, theory, or low-quality studies.
• Nonsense: Approaches that have been rigorously tested and proven not to work, despite continued popularity and marketing.

I’d place PRP in the promising category.

Let’s wrap it up with a couple important things…

1. This newsletter and podcast are completely free. I spend many hours each week researching, writing, illustrating, recording, editing, and uploading. The best way you can support it and allow it to continue is to share it with people you know. You can just send them to ​gtperformance.co/newsletter​ and they can subscribe there!
2. Everything in these newsletters, podcasts, social media, and on our website is for educational purposes only and should not be taken as medical advice for you or your athlete. Consult directly with a healthcare professional.

Thanks so much for your help in spreading the word about athlete development!

Be >,

Zach

Dr. Zach Guiser, PT, DPT, CSCS