PRP Knee Injection : We Know More about PRP than Knee Replacement

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If you’re considering a PRP knee injection the first question to ask is whether we know this procedure works. Given that many patients want PRP injections to avoid a knee replacement, let’s focus on whether PRP injections work as well as, worse, or better than knee replacement by looking at the research behind each.

What is PRP?

PRP stands for Platelet-Rich Plasma. This is a product made from your own blood where your platelets are concentrated in your plasma. Platelets contain healing growth factors that release their payloads over time to assist in tissue repair (1).

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What is a PRP Knee Injection Used For?

A PRP knee injection is usually used to help arthritis pain. The procedure typically involves using ultrasound or real-time x-ray imaging (fluoroscopy) to precisely inject PRP into the damaged knee joint. The knee will sometimes be swollen for a few days and then most patients respond by a few weeks. These injections can provide pain relief and improve knee function for 1-2 years in most patients. Also different than steroid injections which can harm knee cartilage (4, 22), PRP knee injection is thought to help knee cartilage (2).

Understanding Medical Research

Medical research can be graded like a report card (3). The studies that are randomized controlled trials (RCT) get higher grades than other types of research. The absolute best type of research is one where a fake or sham treatment is used and neither the doctor nor patient knows who got which treatment. For surgeries this is more difficult, so for sham procedure studies, usually only the patient doesn’t know if they got the real surgery or one that was faked.

How Good is the Research Showing that PRP Works?

We have 27 RCTs to date on PRP knee injection when used to treat arthritis. Those are studies that compared PRP to common treatments like steroid shots, hyaluronic acid (HA) injections (knee gel shots), or physical therapy (5-21). PRP was as good as HA or better and better than steroid shots or exercise. We even have studies that show that PRP works when compared to a faked treatment like saline.

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How Does PRP Knee Arthritis Research Compare to Knee Replacement?

You may not have a sense that 27 RCTs showing that PRP knee injection works for arthritis is a good amount, so let’s compare that amount and quality of research to a common treatment for knee arthritis. We have more than 600,000 knee replacement surgeries in the US that happen each year at an approximate cost of $49,500 each or approximately 30 billion. So how many RCTs do we have on knee replacement? Two. In fact, unlike most of the PRP RCTs shown above, neither of these was a higher quality sham study. Meaning the patients knew they were getting a knee replacement, which in and of itself would be a huge placebo effect. Meaning, big surgeries have the effect of convincing people they must be better even when the surgery didn’t help at all (24).

In one of these two studies (23), the results of knee replacement weren’t impressive. meaning, you needed to replace 5-6 knees to ensure that one patient reported a 15% functional improvement or better. 3 in 4 of the patients who were randomized to get physical therapy over knee replacement ended up canceling their surgery. Hence, when compared head to head, we have much more high-quality information showing that PRP works when compared to knee replacement.

Is PRP Knee Injection Covered by Insurance?

For most Americans, the answer is not yet. While certain groups like Regenexx (author of this blog post) have gotten coverage from many self-insured employers, that coverage right now extends to only about 10% of the total patients with private health insurance. Why then is a knee replacement covered? Instuitional inertia is the only answer that makes sense.

The upshot? PRP knee injection should be a real contender when you have knee arthritis. We’ve been using this treatment for 15 years with great success and the research now backs up that it works.



(1) Alves R, Grimalt R: A Review of Platelet-Rich Plasma: History, Biology, Mechanism of Action, and Classification. Skin Appendage Disord 2018;4:18-24. doi: 10.1159/000477353

(2) Cook CS, Smith PA. Clinical Update: Why PRP Should Be Your First Choice for Injection Therapy in Treating Osteoarthritis of the Knee. Curr Rev Musculoskelet Med. 2018;11(4):583–592. doi:10.1007/s12178-018-9524-x

(3) Atkins D, Best D, Briss PA, et al. Grading quality of evidence and strength of recommendations. BMJ. 2004;328(7454):1490. doi: 10.1136/bmj.328.7454.1490

(4) Ammar TY, Pereira TA, Mistura SL, Kuhn A, Saggin JI, Lopes Júnior OV. Viscosupplementation for treating knee osteoarthrosis: review of the literature. Rev Bras Ortop. 2015;50(5):489–494. Published 2015 Aug 5. doi: 10.1016/j.rboe.2015.07.007

(5) Uslu Güvendi E, Aşkin A, Güvendi G, Koçyiğit H. Comparison of Efficiency Between Corticosteroid and Platelet Rich Plasma Injection Therapies in Patients With Knee Osteoarthritis. Arch Rheumatol. 2017;33(3):273–281. Published 2017 Nov 2. doi: 10.5606/ArchRheumatol.2018.6608

(6) Tavassoli M, Janmohammadi N, Hosseini A, Khafri S, Esmaeilnejad-Ganji SM. Single- and double-dose of platelet-rich plasma versus hyaluronic acid for treatment of knee osteoarthritis: A randomized controlled trial. World J Orthop. 2019;10(9):310–326. Published 2019 Sep 18. doi: 10.5312/wjo.v10.i9.310

(7) Joshi Jubert N, Rodríguez L, Reverté-Vinaixa MM, Navarro A. Platelet-Rich Plasma Injections for Advanced Knee Osteoarthritis: A Prospective, Randomized, Double-Blinded Clinical Trial. Orthop J Sports Med. 2017;5(2):2325967116689386. Published 2017 Feb 13. doi: 10.1177/2325967116689386

(8) Raeissadat SA, Rayegani SM, Hassanabadi H, et al. Knee Osteoarthritis Injection Choices: Platelet- Rich Plasma (PRP) Versus Hyaluronic Acid (A one-year randomized clinical trial). Clin Med Insights Arthritis Musculoskelet Disord. 2015;8:1–8. Published 2015 Jan 7. doi: 10.4137/CMAMD.S17894

(9) Montañez-Heredia E, Irízar S, Huertas PJ, et al. Intra-Articular Injections of Platelet-Rich Plasma versus Hyaluronic Acid in the Treatment of Osteoarthritic Knee Pain: A Randomized Clinical Trial in the Context of the Spanish National Health Care System. Int J Mol Sci. 2016;17(7):1064. Published 2016 Jul 2. doi: 10.3390/ijms17071064

(10) Görmeli G, Görmeli CA, Ataoglu B, Çolak C, Aslantürk O, Ertem K. Multiple PRP injections are more effective than single injections and hyaluronic acid in knees with early osteoarthritis: a randomized, double-blind, placebo-controlled trial. Knee Surg Sports Traumatol Arthrosc. 2017 Mar;25(3):958-965. doi: 10.1007/s00167-015-3705-6.

(11) Lana JF, Weglein A, Sampson SE, et al. Randomized controlled trial comparing hyaluronic acid, platelet-rich plasma and the combination of both in the treatment of mild and moderate osteoarthritis of the knee. J Stem Cells Regen Med. 2016;12(2):69–78.

(12) Tavassoli M, Janmohammadi N, Hosseini A, Khafri S, Esmaeilnejad-Ganji SM. Single- and double-dose of platelet-rich plasma versus hyaluronic acid for treatment of knee osteoarthritis: A randomized controlled trial. World J Orthop. 2019;10(9):310–326. Published 2019 Sep 18. doi: 10.5312/wjo.v10.i9.310

(13) Lin KY, Yang CC, Hsu CJ, Yeh ML, Renn JH. Intra-articular Injection of Platelet-Rich Plasma Is Superior to Hyaluronic Acid or Saline Solution in the Treatment of Mild to Moderate Knee Osteoarthritis: A Randomized, Double-Blind, Triple-Parallel, Placebo-Controlled Clinical Trial. Arthroscopy. 2019 Jan;35(1):106-117. doi: 10.1016/j.arthro.2018.06.035.

(14) Huang Y, Liu X, Xu X, Liu J. Intra-articular injections of platelet-rich plasma, hyaluronic acid or corticosteroids for knee osteoarthritis : A prospective randomized controlled study. Orthopade. 2019 Mar;48(3):239-247. doi: 10.1007/s00132-018-03659-5.

(15) Di Martino A, Di Matteo B, Papio T, Tentoni F, Selleri F, Cenacchi A, Kon E, Filardo G. Platelet-Rich Plasma Versus Hyaluronic Acid Injections for the Treatment of Knee Osteoarthritis: Results at 5 Years of a Double-Blind, Randomized Controlled Trial. Am J Sports Med. 2019 Feb;47(2):347-354. doi: 10.1177/0363546518814532.

(16) Yu W, Xu P, Huang G, Liu L. Clinical therapy of hyaluronic acid combined with platelet-rich plasma for the treatment of knee osteoarthritis. Exp Ther Med. 2018;16(3):2119–2125. doi: 10.3892/etm.2018.6412

(17) Buendía-López D, Medina-Quirós M, Fernández-Villacañas Marín MÁ. Clinical and radiographic comparison of a single LP-PRP injection, a single hyaluronic acid injection and daily NSAID administration with a 52-week follow-up: a randomized controlled trial. J Orthop Traumatol. 2018;19(1):3. Published 2018 Aug 20. doi: 10.1186/s10195-018-0501-3

(18) Su K, Bai Y, Wang J, Zhang H, Liu H, Ma S. Comparison of hyaluronic acid and PRP intra-articular injection with combined intra-articular and intraosseous PRP injections to treat patients with knee osteoarthritis. Clin Rheumatol. 2018 May;37(5):1341-1350. doi: 10.1007/s10067-018-3985-6.

(19) Louis ML, Magalon J, Jouve E, Bornet CE, Mattei JC, Chagnaud C, Rochwerger A, Veran J3, Sabatier F. Growth Factors Levels Determine Efficacy of Platelets Rich Plasma Injection in Knee Osteoarthritis: A Randomized Double Blind Noninferiority Trial Compared With Viscosupplementation. Arthroscopy. 2018 May;34(5):1530-1540.e2. doi: 10.1016/j.arthro.2017.11.035.

(20) Lisi C, Perotti C, Scudeller L, Sammarchi L, Dametti F, Musella V, Di Natali G. Treatment of knee osteoarthritis: platelet-derived growth factors vs. hyaluronic acid. A randomized controlled trial. Clin Rehabil. 2018 Mar;32(3):330-339. doi: 10.1177/0269215517724193

(21) Cole BJ, Karas V, Hussey K, Pilz K, Fortier LA. Hyaluronic Acid Versus Platelet-Rich Plasma: A Prospective, Double-Blind Randomized Controlled Trial Comparing Clinical Outcomes and Effects on Intra-articular Biology for the Treatment of Knee Osteoarthritis. Am J Sports Med. 2017 Feb;45(2):339-346. doi: 10.1177/0363546516665809.

(22) Kompel AJ, Roemer FW, Murakami AM, Diaz LE, Crema MD, Guermazi A. Intra-articular Corticosteroid Injections in the Hip and Knee: Perhaps Not as Safe as We Thought? Radiology. 2019 Dec;293(3):656-663. doi: 10.1148/radiol.2019190341.

(23) Skou S, Roos E, Laursen M, Rathleff M,  Arendt-Nielsen L, Simonsen O, Rasmussen S. A Randomized, Controlled Trial of Total Knee Replacement. N Engl J Med 2015; 373:1597-1606. DOI: 10.1056/NEJMoa1505467

(24) (2) Wartolowska K, Judge A, Hopewell S, et al. Use of placebo controls in the evaluation of surgery: systematic review. BMJ. 2014;348:g3253. Published 2014 May 21. doi: 10.1136/bmj.g3253

Chris Centeno, MD is a specialist in regenerative medicine and the new field of Interventional Orthopedics. Centeno pioneered orthopedic stem cell procedures in 2005 and is responsible for a large amount of the published research on stem cell use for orthopedic applications. View Profile

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NOTE: This blog post provides general information to help the reader better understand regenerative medicine, musculoskeletal health, and related subjects. All content provided in this blog, website, or any linked materials, including text, graphics, images, patient profiles, outcomes, and information, are not intended and should not be considered or used as a substitute for medical advice, diagnosis, or treatment. Please always consult with a professional and certified healthcare provider to discuss if a treatment is right for you.

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