PRP blood shots aren’t prepared the same way everywhere

More white blood cells may mean more soreness afterward

Clinics don’t all start with the same amount of blood. They can also finish with different amounts of platelet-rich liquid. Some PRP keeps more white blood cells, while some keeps fewer. The mix with more white cells has often caused extra swelling and soreness after a knee shot. A mix with fewer has often been gentler on knees. Tendon findings can differ. A knee study using fewer white cells can’t tell you how your tendon will respond to a mix with more.

The letters PRP don’t tell you what’s in the tube.

The exam must find the sore tissue before the shot is discussed

The provider needs to learn whether your ache sits inside the joint or in a tendon. Another cause may need different care. Take any X-ray report you already have. Tell the provider about aspirin, blood thinners, and anti-inflammatory drugs you use often. Don’t stop a prescribed drug on your own. At QC Kinetix, medical providers are staff trained to examine you; their non-surgical regenerative treatments include PRP drawn and spun from your blood. They can discuss whether it fits the exam findings.

Without a clear cause, there isn’t a clear reason for PRP.

Clear answers should come before payment

Ask which body part the provider thinks is sore and why. Ask whether the PRP will contain more or fewer white blood cells. Find out how many procedures are proposed and what follow-up comes with the cost. You’ll also need plain limits for work, walking, and exercise afterward. The clinic can’t know your result ahead of time. A sure-sounding sales pitch doesn’t change that. PRP hasn’t been shown to rebuild worn cartilage, so its value can’t rest on a promise of a new-looking joint.

If the answers aren’t clear, you can wait.

Sources

1. The DEPA classification was built because platelet and leukocyte counts alone do not describe an injection. Applied retrospectively to 20 published PRP preparations, the dose of injected platelets ranged from 0.21 billion to 5.43 billion - a 25-fold spread. No device recovered more than 90% of the platelets in the blood drawn, and most preparations were contaminated with red blood cells: only three of the devices reached a purity score corresponding to more than 90% platelets relative to red cells and leukocytes.

   Magalon J, Chateau AL, Bertrand B, et al. — DEPA classification: a proposal for standardising PRP use and a retrospective application of available devices. BMJ Open Sport & Exercise Medicine, 2016. DOI: 10.1136/bmjsem-2015-000060.

2. A systematic review and meta-analysis of adverse events in randomized trials of intra-articular PRP for knee osteoarthritis found PRP associated with mild, transient adverse events - knee pain and swelling - that typically resolve without intervention, and more frequent with LEUKOCYTE-RICH formulations. Leukocyte-poor PRP had a safety profile similar to hyaluronic acid. Knee stiffness was more frequent with PRP than with normal saline (P=.031). No severe adverse events were reported in any group.

   Nakagawa HF, Kim J, Rabinowitz J, et al. — Assessment of adverse events and safety associated with intra-articular platelet-rich plasma injections compared to other injectates for knee osteoarthritis: A systematic review and meta-analysis. PM&R, 2026. DOI: 10.1002/pmrj.70141.

3. In the RESTORE trial - the largest placebo-controlled PRP trial in knee osteoarthritis - 288 adults aged 50+ with symptomatic Kellgren-Lawrence grade 2-3 medial knee OA received three weekly intra-articular injections of leukocyte-poor PRP from a commercial system or saline placebo. At 12 months the mean change in knee pain was -2.1 points with PRP versus -1.8 with saline (difference -0.4; 95% CI -0.9 to 0.2; P=.17) against a minimum clinically important difference of 1.8, and the change in medial tibial cartilage volume was -1.4% versus -1.2% (difference -0.2%; 95% CI -1.9% to 1.5%; P=.81). Twenty-nine of 31 prespecified secondary outcomes showed no significant between-group difference. The authors concluded the findings do not support use of PRP for knee OA.

   Bennell KL, Paterson KL, Metcalf BR, et al. — Effect of Intra-articular Platelet-Rich Plasma vs Placebo Injection on Pain and Medial Tibial Cartilage Volume in Patients With Knee Osteoarthritis: The RESTORE Randomized Clinical Trial. JAMA, 2021. DOI: 10.1001/jama.2021.19415.

4. The devices used to spin PRP at the point of care are cleared by FDA as clinical centrifuges, product code JQC, a Class I device under 21 CFR 862.2050 - for example the Biomet GPS Platelet Separation Kit (K030555, cleared 2003) and the Harvest SmartPrep2 / SmartPrep Platelet Concentration System (K103340, cleared 2010). That clearance covers the equipment that separates blood. It is not an FDA approval of platelet-rich plasma as a treatment for osteoarthritis, tendinopathy or any other orthopedic condition, and copy must never blur the two.

   U.S. Food and Drug Administration (Center for Devices and Radiological Health) — 510(k) Premarket Notification database and Product Classification: JQC, Centrifuges (Micro, Ultra, Refrigerated) For Clinical Use, 21 CFR 862.2050. FDA accessdata (CDRH device databases), 2003.

5. A randomized double-blind trial of 80 patients with chronic gluteal tendinopathy (lateral hip pain) compared a single ultrasound-guided PRP injection with a single corticosteroid injection. At 12 weeks the PRP group had significantly better modified Harris Hip Scores (P=.048), and 82% versus 56.7% of patients reached the minimal clinically important difference (P=.016).

   Fitzpatrick J, Bulsara MK, O'Donnell J, et al. — The Effectiveness of Platelet-Rich Plasma Injections in Gluteal Tendinopathy: A Randomized, Double-Blind Controlled Trial Comparing a Single Platelet-Rich Plasma Injection With a Single Corticosteroid Injection. American Journal of Sports Medicine, 2018. DOI: 10.1177/0363546517745525.

6. Two-year follow-up of the same 80-patient gluteal tendinopathy trial found the single leukocyte-RICH PRP injection produced improvement that was sustained at 104 weeks (mHHS 53.77 at baseline to 82.59 at two years; P<.0001), whereas the corticosteroid improvement peaked at six weeks and was not maintained beyond 24 weeks. This is one of the clearest demonstrations that leukocyte-rich PRP is the formulation with evidence in TENDON, not in cartilage.

   Fitzpatrick J, Bulsara MK, O'Donnell J, et al. — Leucocyte-Rich Platelet-Rich Plasma Treatment of Gluteus Medius and Minimus Tendinopathy: A Double-Blind Randomized Controlled Trial With 2-Year Follow-up. American Journal of Sports Medicine, 2019. DOI: 10.1177/0363546519826969.