What do white cells change in PRP?

What does leukocyte-rich vs leukocyte-poor PRP mean?

Leukocyte-rich means the prepared blood portion keeps more white cells. Leukocyte-poor means most of those white cells have been reduced. The labels describe what is in the prepared blood portion. White cells take part when the body responds to an injury.

They don't tell you by themselves whether the treatment will help. Preparation methods can also change the platelet amount and other blood parts. Ask the clinic which kind it uses and why.

Does the sore body part matter?

Research on joints often uses preparations with fewer white cells. Tendon research sometimes uses preparations that keep more white cells. The findings still differ by the tendon and the study.

A sore knee is not the same question as a sore elbow tendon. Even two sore shoulders may have different causes. An exam needs to identify which tissue is hurting before treatment is discussed. So the exam must name the painful body part and tissue clearly.

What should you ask at the visit?

Have the medical provider describe the exam findings to you. Find out whether the soreness seems to come from cartilage, a tendon, or another joint part. Ask why the proposed preparation matches that finding. Write the answer down so you can compare it after the visit.

Tell the clinic about medicines and any past reaction after a procedure. Ask what soreness is expected afterward and whom to call about a change. QC Kinetix offers regenerative treatments, care based on a patient’s blood components, as a non-surgical option discussed by licensed clinic staff.

Evidence sources

1. A Bayesian network meta-analysis of nine studies (six RCTs, 1055 patients) found leukocyte-POOR PRP produced significantly better WOMAC scores than hyaluronic acid (mean difference -21.14; 95% CI -39.63 to -2.65) and than placebo (-17.84; 95% CI -34.95 to -0.73), while leukocyte-RICH PRP showed no such significant difference versus placebo. PRP of either type caused more local adverse reactions than hyaluronic acid (OR 5.63; 95% CI 1.38-22.90), almost always local swelling and pain, with no difference in safety between the two PRP types.

   Riboh JC, Saltzman BM, Yanke AB, et al. — Effect of Leukocyte Concentration on the Efficacy of Platelet-Rich Plasma in the Treatment of Knee Osteoarthritis. American Journal of Sports Medicine, 2016.

2. A narrative review of PRP concluded that the literature suggests leukocyte-rich PRP is more beneficial in tendinopathies while pure (leukocyte-poor) PRP is more beneficial in cartilage pathology - but stated plainly that different PRP preparations have not been directly compared head-to-head in ANY pathology, and that the PRP type used is frequently not even stated in published research.

   Collins T, Alexander D, Barkatali B — Platelet-rich plasma: a narrative review. EFORT Open Reviews, 2021.

3. In a controlled laboratory study, blood from five healthy donors was processed through three commercial PRP systems (MTF Cascade, Arteriocyte Magellan, Biomet GPS III). Platelet, red-cell and TGF-beta1 concentrations did not differ significantly between systems, but white-cell counts and PDGF-alpha-beta, PDGF-beta-beta and VEGF concentrations differed significantly across all three. Cascade produced leukocyte-poor PRP while GPS III and Magellan produced leukocyte-rich PRP with correspondingly higher white cells and growth factors.

   Castillo TN, Pouliot MA, Kim HJ, et al. — Comparison of growth factor and platelet concentration from commercial platelet-rich plasma separation systems. American Journal of Sports Medicine, 2011.

4. Three healthy adults each donated 181 mL of blood which was processed through four commercial PRP kits (GPS III, Smart-Prep2, Magellan, ACP). The three kits that draw from the buffy-coat layer produced platelet concentrations 3-6 times baseline and white-cell concentrations 3-6 times baseline; the one kit drawing from plasma produced platelet concentrations only 1.5 times baseline. The authors concluded that the lack of standardisation of PRP preparation has contributed, at least in part, to the varying clinical efficacy reported for PRP.

   Fitzpatrick J, Bulsara MK, McCrory PR, et al. — Analysis of Platelet-Rich Plasma Extraction: Variations in Platelet and Blood Components Between 4 Common Commercial Kits. Orthopaedic Journal of Sports Medicine, 2017.

5. A scoping review of PRP for knee and hip osteoarthritis reported that PRP for knee OA gives clinically comparable or superior outcomes to other injection treatments, that the evidence in HIP osteoarthritis is far less consistent, and that evidence is lacking to show the presence of leukocytes significantly influences clinical outcomes. It named leukocyte concentration, OA grade and formulation comparability as the open questions.

   Tanguilig G, Dhillon J, Kraeutler MJ, et al. — Platelet-Rich Plasma for Knee and Hip Osteoarthritis Pain: A Scoping Review. Current Reviews in Musculoskeletal Medicine, 2024.

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.

7. A three-arm randomized controlled trial added leukocyte-rich PRP, leukocyte-poor PRP or nothing to arthroscopic rotator cuff repair. At 12 months there were no significant differences between the three groups in functional scores, overall retear rate (8% across the study) or complications; LR-PRP showed better ASES scores than control at 3 and 6 months only, and the authors described its clinical benefit as remaining to be proven.

   Yao L, Pang L, Zhang C, et al. — Platelet-Rich Plasma for Arthroscopic Rotator Cuff Repair: A 3-Arm Randomized Controlled Trial. American Journal of Sports Medicine, 2024.

8. 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.

9. A systematic review of 26 studies of PRP for lateral epicondylitis assessed against minimal clinically important difference thresholds rather than statistical significance found the mean improvement exceeded the MCID from week 4 through week 104 for VAS and DASH, and from weeks 4-52 for the Mayo score. Both leukocyte-rich and leukocyte-poor systems met the MCID at almost every observation point.

   Niemiec P, Szyluk K, Jarosz A, et al. — Effectiveness of Platelet-Rich Plasma for Lateral Epicondylitis: A Systematic Review and Meta-analysis Based on Achievement of Minimal Clinically Important Difference. Orthopaedic Journal of Sports Medicine, 2022.

10. 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.

11. The ESSKA-ICRS consensus applied the RAND/UCLA appropriateness method to 216 clinical scenarios for intra-articular PRP in knee OA. Only 84 scenarios (38.9%) were rated appropriate, 9 (4.2%) inappropriate and 123 (56.9%) uncertain. PRP was judged appropriate in patients aged 80 or under with KL grade 0-III osteoarthritis AFTER failed conservative non-injective or injective treatment; it was NOT considered appropriate as a first treatment, nor in KL grade IV (bone-on-bone) osteoarthritis, where 91.7% and 87.5% of scenarios respectively were uncertain.

    Kon E, de Girolamo L, Laver L, et al. — Platelet-rich plasma injections for the management of knee osteoarthritis: The ESSKA-ICRS consensus. Recommendations using the RAND/UCLA appropriateness method for different clinical scenarios. Knee Surgery, Sports Traumatology, Arthroscopy, 2024.

12. The American Academy of Physical Medicine and Rehabilitation convened a technical expert panel that ran a structured literature review (2023, updated through June 2025) and a modified Delphi process, and issued five evidence-based clinical recommendations plus 11 consensus-based best practices for PRP in knee osteoarthritis. The statement is explicit that orthobiologic therapies 'remain an evolving area of practice' and that robust, dose-dependent randomized controlled trials are still needed to establish PRP's clinical effects.

    Borg-Stein J, Jayaram P, Colorado BS, et al. — AAPM&R guidance statement on platelet rich plasma for knee osteoarthritis. PM&R, 2026.