# What is in platelet-rich plasma (PRP), and why does the amount matter? *What is in PRP? | PRP injections Scottsdale* > For prp injections scottsdale, learn what PRP contains, why white blood cells matter and what knee studies found about amount. PRP starts with blood drawn from you. Fast spinning sorts the blood into separate parts. The kept part has extra platelets. These tiny cells help clot a cut and begin the body's repair response. The amount of liquid and platelet count aren't the same. Think about coffee in a cup. Cup size tells you the amount, not its strength. PRP also needs both numbers before you know its platelet dose. ## Which PRP type is easier on a joint? One PRP type keeps more white blood cells. Another removes most of them. A 2026 knee review found brief soreness and swelling more often with the white-cell-rich type. It didn't show that this type worked better. Some tendon studies use PRP with more white cells. Many joint studies use the type with fewer. Research hasn't proved one best type for every body part. Ask which type the clinic plans to use and why. ## What amount helped knees in studies? A 2025 review compared knee trial groups by platelet dose. Groups reporting better knee scores received about 5.5 billion platelets. Groups without a positive difference received about 2.3 billion. That split didn't disappear at 12 months. The finding suggests the total platelet count could matter. It doesn't set one right amount for you. The studies also differed in joint damage and care used with PRP. Research for other body parts can't yet name a useful amount. ## What can I ask before deciding? A medical provider is the QC Kinetix worker who examines the sore area. The site gives no exact job title. Ask the clinic what license the examiner holds. The clinic offers regenerative treatments, meaning non-surgical care using a separated layer of your blood. Ask for the planned platelet count and white-cell type. Then ask how many procedures are planned. Mention blood thinners and blood problems before any blood draw. Don't change medicine unless your doctor agrees. ## Sources 1. A systematic review of 29 randomized trials of PRP for knee OA that reported a platelet count, concentration or dose found that the 28 treatment arms with statistically significant positive outcomes at 6 months had a mean platelet dose of 5,500 (+/-474) x 10^6, while the three arms without a positive difference averaged 2,302 (+/-437) x 10^6 (P<.01). The same separation held at 12 months: 5,464 versus 2,253 x 10^6 (P<.05). Berrigan WA, Bailowitz Z, Park A, et al. — [A Greater Platelet Dose May Yield Better Clinical Outcomes for Platelet-Rich Plasma in the Treatment of Knee Osteoarthritis: A Systematic Review](https://pubmed.ncbi.nlm.nih.gov/38513880/). *Arthroscopy*, 2025. DOI: 10.1016/j.arthro.2024.03.018. 2. A systematic review and meta-analysis of platelet dosage across musculoskeletal conditions identified a potential dose-response relationship in knee osteoarthritis, with an apparent threshold above 10 billion platelets for favourable clinical outcomes, and the effect more pronounced for function than for pain. For conditions other than knee OA the authors found the literature too unclear to identify an optimal dose. Berrigan W, Tao F, Kopcow J, et al. — [The Effect of Platelet Dose on Outcomes after Platelet Rich Plasma Injections for Musculoskeletal Conditions: A Systematic Review and Meta-Analysis](https://pubmed.ncbi.nlm.nih.gov/39331322/). *Current Reviews in Musculoskeletal Medicine*, 2024. DOI: 10.1007/s12178-024-09922-x. 3. 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](https://pubmed.ncbi.nlm.nih.gov/39002073/). *Current Reviews in Musculoskeletal Medicine*, 2024. DOI: 10.1007/s12178-024-09916-9. 4. 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](https://pubmed.ncbi.nlm.nih.gov/42101047/). *PM&R*, 2026. DOI: 10.1002/pmrj.70141. 5. A systematic review of 105 clinical PRP studies in orthopaedics published 2006-2016 found that only 11 (10%) described the preparation protocol clearly enough for another investigator to repeat it, and only 17 (16%) reported any quantitative metric of the final PRP composition. The authors concluded that the current reporting of PRP preparation and composition does not allow the PRP products actually delivered to patients to be compared between studies. Chahla J, Cinque ME, Piuzzi NS, et al. — [A Call for Standardization in Platelet-Rich Plasma Preparation Protocols and Composition Reporting: A Systematic Review of the Clinical Orthopaedic Literature](https://pubmed.ncbi.nlm.nih.gov/29040132/). *Journal of Bone and Joint Surgery (American)*, 2017. DOI: 10.2106/JBJS.16.01374. 6. 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](https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPCD/classification.cfm?ID=JQC). *FDA accessdata (CDRH device databases)*, 2003. ## Would an exam help you decide? Take your medicine names, prior reports, and brief notes on the ache. Someone at the clinic will examine the sore area. You can ask what is in the prepared blood treatment. Also ask how recovery could affect your usual day. Book a free consultation: --- Straight answers for joint soreness Plain help for sore joints, warning signs, PRP facts and what happens at QC Kinetix. Plain health information about sore joints, PRP, warning signs and the Scottsdale clinic. This site is operated by the owners of the QC Kinetix Phoenix-area clinics, including the Scottsdale location it recommends, and those owners benefit when a reader books a consultation. Copyright 2026 Scottsdale PRP Field Guide. General health education, not medical advice for an individual diagnosis.