Connectivity with Iain Duncan

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Iain Duncan Update July 2020

Based on a number of studies and our own experience there are benefits from doing repeated or cycling PRP injections for osteoarthritis of the knee. One such study showed PRP injections led to a significant reduction in pain and improvement in function after 12 months, which can be further improved at 18 months by annual repetition of the treatment. Although the beneficial effects are ill sustained at 2 years, the results are encouraging when compared to the pre-treatment function [1]. Another study [2] over 5yrs compared HA and PRP and concluded “both treatments were effective in improving knee functional status and symptoms over time”. Of particular note:

the median duration of patient subjective perception of symptomatic relief was 9 months for HA and 12 months for PRP

A major metanalysis just published [3] in Arthroscopy looked at level I randomised controlled trials comparing hyaluronic acid and PRP. They found 26 trials that met their criteria and concluded:

“For the nonsurgical treatment of KOA, compared with HA, intra-articular injection of PRP could significantly reduce patients’ early pain and improve function. There was no significant difference in adverse events between the two groups. PRP was more effective than HA in the treatment of KOA, and the safety of these two treatment options was comparable.”

See my extended list of PRP references here.

  1. Gobbi, A., Lad, D. & Karnatzikos, G. The effects of repeated intra-articular PRP injections on clinical outcomes of early osteoarthritis of the knee. Knee Surg Sports Traumatol Arthrosc 23, 2170–2177 (2015).
  2. Di Martino A, Di Matteo B, Papio T, et al. 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;47(2):347-354.
  3. Tan J, Chen H, Zhao L, Huang W. Platelet Rich Plasma Versus Hyaluronic Acid in the Treatment of Knee Osteoarthritis: a Meta-Analysis of 26 randomized controlled trials [published online ahead of print, 2020 Jul 14]. Arthroscopy. 2020;S0749-8063(20)30604-6. doi:10.1016/j.arthro.2020.07.011


Iain Duncan Update February 2018

This recent randomised double blind placebo controlled trail has shown eunequivocal benefit of PRP for OA knees2.

Trial Design:

  • A total of 162 patients with different stages of knee OA were randomly divided into four groups: each had 3 injections each: 3 IA doses of PRP, one dose of PRP, 3 inj of HA (hyaluronic acid) or a saline injection (control).
  • Two subgroups: early OA (Kellgren–Lawrence grade 0 with cartilage degeneration or grade I–III) and advanced OA (Kellgren–Lawrence grade IV).
  • The patients were evaluated before the injection and at the 6-month follow- ups using the EuroQol visual analogue scale (EQ-VAS) and International Knee Documentation Committee (IKDC) subjective scores.


  • There was a statistically significant improvement in the IKDC and EQ-VAS scores in all the treatment groups compared with the control group.
  • The knee scores of patients treated with three PRP injections were significantly better than those patients of the other groups. There was no significant difference in the scores of patients injected with one dose of PRP or HA.
  • In the early OA subgroups, significantly better clinical results were achieved in the patients treated with three PRP injections, but there was no significant difference in the clinical results of patients with advanced OA among the treatment groups.


  1. The clinical results of this study suggest intra-articular PRP and HA treatment for all stages of knee OA.
  2. For patients with early OA, multiple (3) PRP injections are useful in achieving better clinical results.
  3. For patients with advanced OA, multiple injections do not significantly improve the results of patients in any group.


  1. Sheth U; Dwyer T; Smith I; Wasserstein D; Theodoropoulos J; Takhar S; Chahal J. Does Platelet-Rich Plasma Lead to Earlier Return to Sport When Compared With Conservative Treatment in Acute Muscle Injuries? A Systematic Review and Meta-analysis. Arthroscopy.  2015; 31(11):2213-21
  2. Görmeli et al (2017). 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 Surgery, Sports Traumatology, Arthroscopy,25(3), 958–965.

Iain Duncan Update August 2017

A recent trial and more experience with the use of PRP has prompted me to do this brief update on PRP therapy for knees.

I came across a further review in Arthroscopy1 from that concluded PRP “is a viable treatment for knee OA and has the potential to lead to symptomatic relief for up to 12 months”. Furthermore intra-articular PRP therapy “offers better symptomatic relief to patients with early knee degenerative changes, and its use should be considered in patients with knee OA”.

PRP for knee osteoarthritis

We have now successfully undertaken a series of PRP injections in OA knee and most have had more advanced disease than is ideal (the best responders have the least radiological changes), but ~80% have had longer and better responses to PRP than earlier intra-articulator corticosteroid treatments. This is a similar response rate to tendon tears.

Iain Duncan February 2016

I understand the rationale and use of platelet rich plasma (PRP) for tendon problems but I am continually asked about PRP injections for osteoarthritis.  It is less intuitive than its use for tendon pathologies, where the PRP can be seen to simulate a normal healing response. PRP is not “normal” in joints and therefore its use is not entirely rational.

I have certainly done injections of PRP into both knees and hip for osteoarthritis(OA). Anecdotally in the few cases I have done there has been a universal improvement in symptoms, but it is too early to know whether there will be any longer term benefit. The results of studies using PRP for OA are comprehensively summarised in this paper by Filardo et al in this study from 2015: Platelet-rich plasma: why intra-articular? A systematic review of preclinical studies and clinical evidence on PRP for joint degeneration.

PRP injections for osteoarthritis

They conclude: “Besides the limits and sometimes controversial findings, the preclinical literature shows an overall support toward this PRP application. An intra-articular injection does not just target cartilage; instead, PRP might influence the entire joint environment, leading to a shortterm clinical improvement. Many biological variables might influence the clinical outcome and have to be studied to optimize PRP injective treatment of cartilage degeneration and osteoarthritis.”

Any earlier assessment of PRP therapy in Osteoarthritis of the knee was done by the Health Policy Advisory Committee on Technology  in August 2013 and the full document can be downloaded here. That review of the literature at that time concluded in its summary “All studies included in this assessment reported short-term improvements in function and a decrease in pain scores; however this effect did not appear to be sustained over a long period of time. The procedure appears to be safe, with the only adverse event reported being short-term pain following injection due to inflammation.”

It is likely that over the next few years better data will be available and we will discover whether the benefit is only short-term, or whether it reduces or delays the need for surgical intervention. On the plus side no significant adverse effects have been documented and the cost is less than many other interventions. Even if its net effect is only to delay surgery many patients will consider this a worthwhile outcome.