Hyaluronic Acid Injections and How They Compare to PRP
Hyaluronic acid injection, also called viscosupplementation, places a gel-like fluid into an arthritic joint. Hyaluronic acid occurs naturally in joint fluid and contributes to lubrication and shock absorption. In an arthritic knee, both the amount and the quality of that fluid change. Viscosupplementation is an attempt to replace some of what has been lost.
It has been in use for decades, it is familiar to most patients who have been treated for knee arthritis, and it is frequently the first injection a patient is offered after cortisone. That familiarity is the reason this page exists.
Where hyaluronic acid fits in our practice
We use viscosupplementation rarely. It is not our default treatment for knee arthritis, and the reason is set out in the evidence below. We use hyaluronic acid when clinically indicated, and that is the exception rather than the routine.
What we perform routinely for knee arthritis is high-dose platelet-rich plasma and bone marrow aspirate concentrate. Every orthobiologic injection we perform is autologous, prepared from your own tissue on the day of treatment and delivered under ultrasound guidance.
Patients ask us how hyaluronic acid compares. Rather than avoid the question, this page answers it from the published evidence.
How hyaluronic acid compares with high-dose PRP for knee arthritis
The largest synthesis of head-to-head data is a 2021 systematic review and meta-analysis in the American Journal of Sports Medicine covering 18 Level I randomized controlled trials and 1,608 patients. Mean improvement in total WOMAC score was 44.7 percent with PRP compared with 12.6 percent with hyaluronic acid. The authors concluded that patients treated for knee osteoarthritis with PRP can be expected to experience improved clinical outcomes compared with hyaluronic acid.
A separate double-blind randomized trial is worth reading alongside it, because it did something most trials do not: it specified the dose. Patients received PRP containing an absolute count of 10 billion platelets in 8 mL, compared against hyaluronic acid. At one year the PRP group had better WOMAC and IKDC scores and walked substantially further in a six-minute pain-free walking test.
The honest caveat is that individual trials do not all agree. A 2017 double-blind randomized trial of 111 patients found no difference between hyaluronic acid and PRP in its primary outcome measure, while secondary measures including IKDC and visual analogue pain scores favoured PRP at 24 and 52 weeks. A page that quoted only the trials that agreed with us would not be worth reading.
Why dose is the variable that keeps appearing
PRP is not one thing. Platelet concentration, total platelet dose, leukocyte content and volume all differ between systems, and most published trials do not report them. When a trial specifies a high absolute platelet dose, the results tend to separate from hyaluronic acid more clearly than when the dose is unstated.
That is the practical reason we measure and record the platelet dose for every PRP treatment we perform, and why we do not treat "PRP" as a single interchangeable product.
Combining hyaluronic acid with orthobiologics
Current clinical research is evaluating whether hyaluronic acid has a synergistic effect when combined with orthobiologics such as PRP for knee arthritis. The answer so far is specific rather than promising or dismissive.
A 2022 systematic review of combination therapy found that PRP combined with hyaluronic acid was superior to hyaluronic acid alone, but was not superior to PRP alone. In other words, adding hyaluronic acid to PRP has not yet been shown to add anything beyond what the PRP contributes. That may change as further trials are published, and it is an active area of study.
What this means if you have knee arthritis
Hyaluronic acid is a reasonable, long-established treatment and many patients get relief from it. The evidence simply suggests that, used on its own, it does less for knee osteoarthritis than well-dosed platelet-rich plasma does.
If you have already had hyaluronic acid injections and they helped for a while, that history is useful information and worth bringing to your consultation. If they did not help, that is useful too, and it does not predict how you will respond to an orthobiologic injection.
PRP and orthobiologics for the knee covers what we actually do for an arthritic knee, and the orthobiologics overview explains how the treatments differ from each other.
Frequently asked questions
Do you offer hyaluronic acid injections at Texas Orthobiologics?
Rarely. Hyaluronic acid is not our default treatment for knee arthritis and we use it when clinically indicated. For most patients with knee arthritis we recommend high-dose PRP or bone marrow aspirate concentrate instead, for the reasons set out on this page.
Is PRP better than hyaluronic acid for knee arthritis?
For knee osteoarthritis, the weight of Level I evidence favours PRP. A 2021 meta-analysis of 18 Level I randomized trials covering 1,608 patients found mean WOMAC improvement of 44.7 percent with PRP compared with 12.6 percent with hyaluronic acid. Individual trials vary, and at least one well-conducted randomized trial found no difference in its primary outcome measure while secondary measures favoured PRP.
Does the PRP dose matter in these comparisons?
It appears to. A double-blind randomized trial that specified an absolute dose of 10 billion platelets in 8 mL found PRP superior to hyaluronic acid at one year in pain, function and six-minute pain-free walking distance. Trials that do not report platelet dose are difficult to compare with each other, which is one reason we measure the dose on every PRP treatment we perform.
Does adding hyaluronic acid to PRP work better than PRP alone?
Not on the evidence available so far. A 2022 systematic review found that combining PRP with hyaluronic acid was superior to hyaluronic acid alone, but was not superior to PRP alone. Research into whether the two have any synergistic effect is ongoing.
What do you use instead for knee arthritis?
For most patients, high-dose platelet-rich plasma or bone marrow aspirate concentrate. Both are autologous, prepared from your own blood or bone marrow on the day of treatment, and delivered under ultrasound guidance. Hyaluronic acid remains available when clinically indicated.
References
- Belk JW, Kraeutler MJ, Houck DA, Goodrich JA, Dragoo JL, McCarty EC. Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Am J Sports Med. 2021;49(1):249–260. View study
- Bansal H, Leon J, Pont JL, et al. Platelet-rich plasma (PRP) in osteoarthritis (OA) knee: Correct dose critical for long term clinical efficacy. Sci Rep. 2021;11:3971. View study
- Cole BJ, Karas V, Hussey K, Merkow DB, 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;45(2):339–346. View study
- Baria MR, Vasileff WK, Borchers J, et al. Treating Knee Osteoarthritis With Platelet-Rich Plasma and Hyaluronic Acid Combination Therapy: A Systematic Review. Am J Sports Med. 2022;50(1):273–281. View study
