What it is
Platelet-rich plasma (PRP) is made by drawing 15–60 ml of your blood, centrifuging it to concentrate the platelets three- to eight-fold above baseline, and injecting the result into a tendon, a joint, a scalp or a wound. Platelets carry growth factors — PDGF, TGF-β, VEGF, IGF-1 — that are released when they activate, and the idea is to drop a concentrated dose of those signals exactly where repair has stalled.
Two preparation details decide most of the outcome. Leukocyte-rich PRP keeps the white cells and is more inflammatory, which seems to suit chronic tendinopathy; leukocyte-poor PRP removes them and is the form that performs in joints. Platelet concentration, activation method and number of injections vary so much between studies that "PRP" without the recipe is almost meaningless — which is why the trial literature looks contradictory until it is sorted by preparation.
What the research says
| Indication | Evidence grade | What was found |
|---|---|---|
| Lateral epicondylitis (tennis elbow) | Moderate–strong — several RCTs, meta-analyses | Better pain and function than corticosteroid at 6–12 months (Mishra 2014, Gosens 2011); steroid wins at six weeks and loses after. Leukocyte-rich. |
| Knee osteoarthritis | Moderate — many RCTs, meta-analyses | Modest pain and function improvement over hyaluronic acid and saline at 6–12 months, best with leukocyte-poor PRP and a series of three. No cartilage regrowth. One large 2021 trial (Bennell, JAMA) found no difference from saline, so the effect is real but not reliable. |
| Achilles tendinopathy | Strong, and negative — RCT (Kearney 2021, JAMA) | No benefit over sham injection at six months. The clearest "do not bother" in the field. |
| Patellar tendinopathy | Mixed | Some benefit added to an eccentric loading programme; the loading does most of the work. |
| Rotator cuff tears and repair | Early / mixed | Slightly lower re-tear rates when added to surgery in some trials; no clear benefit as an injection alone. |
| Androgenetic hair loss | Moderate — small RCTs, meta-analyses | Increased hair density and thickness after 3–4 monthly scalp sessions versus saline. Effect fades without maintenance. |
| Skin rejuvenation ("vampire facial") | Early | Small split-face studies after microneedling; modest texture change. Cosmetic, not regenerative. |
| Muscle strain, acute injury | Early / negative | Hamstring RCTs show no faster return to play. |
Protocols that are studied
- Knee. Leukocyte-poor PRP, three injections one to two weeks apart, under ultrasound; effect assessed at 6 and 12 months. Single injections perform worse in the meta-analyses.
- Tendon. Leukocyte-rich PRP, one or two injections, with a needle "peppering" of the tendon and a structured eccentric loading programme afterwards. No injection, no corticosteroid, and no anti-inflammatories for about two weeks either side — they blunt the response PRP relies on.
- Scalp. 3–4 sessions a month apart, then maintenance every 3–6 months.
- Rest and loading. 48–72 hours of relative rest, then progressive loading. The rehabilitation is not optional; in the positive tendon trials it is half the treatment.
Who it suits — and who should avoid it
PRP suits chronic tendinopathy that has failed three months of proper loading, mild to moderate knee osteoarthritis in someone not ready for surgery, and early androgenetic thinning. It is low-risk because it is your own blood, which is also why it is widely sold for things it does not help.
- Avoid: platelet disorders and low platelet counts, anticoagulants that cannot be paused, active infection at the site, active cancer, pregnancy, and NSAID use in the two weeks around the injection.
- Expect: pain and swelling for several days after a tendon injection — the inflammatory response is the point. Serious complications (infection, nerve injury) are rare with ultrasound guidance.
- Be sceptical of: PRP for Achilles tendinopathy, acute muscle tears, back pain, and any clinic that cannot tell you the platelet concentration and whether their preparation is leukocyte-rich or poor.
Where it fits in a personal protocol
PRP belongs in the repair block of a plan for a stubborn tendon or a sore knee, scheduled so that the loading programme, the injection and the compounds studied for soft-tissue repair line up. The compounds most often in that conversation are BPC-157 and TB-500 — together, the Wolverine combination — which are studied in animal models for tendon and ligament healing and angiogenesis. The mechanisms (growth-factor release from platelets; peptide signalling on fibroblasts and vessels) are complementary on paper and untested together in people.
Practical placement: a coach usually schedules the PRP series in weeks 2–4 of a twelve-week repair plan, after baseline labs, keeps anti-inflammatories out of that window, and builds the eccentric loading around the injection days. Cold immersion stays away from the injected area for the first week. The immune and inflammation goal page shows the full shape of a repair protocol. The injection is performed by a sports physician or orthopaedic specialist; we do not provide or arrange it.
The hype vs the evidence
- "Regenerates cartilage." No trial shows it. Knee PRP reduces pain and improves function for a season; the joint space does not change.
- "Works for any tendon." Achilles is a well-run negative trial; patellar is mixed; elbow is positive. Indication matters more than the product.
- "One injection fixes it." The knee data favours three; the tendon data needs the loading programme more than the needle.
- What is solid: tennis elbow over steroid at one year, modest knee benefit with leukocyte-poor PRP in a series, and hair density with a maintained schedule.
Frequently asked questions
How long does PRP take to work?
Tendon: pain often gets worse for a week, then improves over two to three months. Knee: benefit builds over six to twelve weeks after the series and typically lasts six to twelve months. Scalp: visible change at three to six months.
Can I combine PRP with BPC-157 or TB-500?
People on a repair protocol often run them in the same block. The compounds are studied in animal models for the same tissues PRP targets; there is no human trial of the combination. Your protocol schedules the timing; your physician does the injection.
Why does the clinic say to stop ibuprofen?
PRP works by triggering a controlled inflammatory repair response. NSAIDs and corticosteroids suppress exactly that, and the tendon trials that allowed them showed smaller effects. Paracetamol is usually fine.
Leukocyte-rich or leukocyte-poor?
Rich for chronic tendons, where a stronger inflammatory kick is wanted; poor for joints, where white cells irritate the synovium. A clinic that cannot tell you which it uses is a reason to find another clinic.
Is PRP worth it for a knee?
For mild to moderate osteoarthritis, a three-injection series of leukocyte-poor PRP gives a modest, temporary improvement in most trials and nothing in some. It is reasonable after weight management and strength work have been tried, and far better value than stem-cell packages.
Want these built into a plan for you?
If a PRP series belongs in your plan, the protocol says which weeks, what loading goes around it and which compounds sit alongside — and your physician does the injection. €399, follow-up included.
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