Recent Advances in Platelet-Rich Plasma Therapy: A Review of the “Strong” Clinical Evidence

Platelet-rich plasma (PRP) is a type of regenerative medicine that is gaining traction and popularity for its excellent safety profile and its positive outcomes in treating musculoskeletal disorders. Prior blog posts have discussed the efficacy of PRP for tendon and ligament injuries and PRP being a non-surgical strategy for joint osteoarthritis. While there are many existing treatments for these painful conditions, ranging from exercise therapy to injections to surgery, PRP is entering the conversation more and more as a helpful and sustainable treatment. The reason for this is the growing body of evidence in medical literature demonstrating PRP’s benefits. 

However, what defines ‘strong’ evidence behind a treatment? Let’s discuss what goes into a good research study and then review a few of the newest and most important, high-quality studies about PRP. 

What is Considered High-Quality Evidence?

Evaluating the quality of a research study could encompass entire textbooks and university-level courses. However, we can describe a few study designs that generally provide the strongest evidence behind any medical treatment, including PRP.  

Randomized Controlled Trials (RCTs)

In RCTs, people are assigned randomly to either a treatment group of interest (e.g., PRP) or a control group (another type of injectable medicine or placebo for comparison). Due to the random selection process, the groups are similar in nearly every way; each group’s characteristics are measured and compared to ensure no significant differences.

After delivering the treatments (such as PRP vs the other options), an outcome such as improvement in pain or ability to perform tasks is measured, and we can see which group got more benefit. A well-done RCT is the gold standard for high-quality evidence in the scientific world because it reduces the chance of biases that can lead to incorrect conclusions.

Prospective Cohort Studies

These studies follow groups (i.e. cohorts) of participants over time to track outcomes and assess the effects of an intervention like PRP versus another type of treatment in a real-world setting. This is different than an RCT because people are not randomized into groups.

Ultimately, these studies help understand long-term benefits and potential side effects. The quality of evidence from these studies is great but slightly below the strength of an RCT.

Systematic Reviews and Meta-Analyses

These are studies that summarize data from multiple studies at the same time. A systematic review looks at all the available studies to see what each concluded and how strong each individual study design was (i.e., which studies showed benefit from PRP and which ones did not), while a meta-analysis combines actual data and numbers from RCTs and other studies to see if there is a broad trend in one direction or another.

However, these studies are only as strong as the evidence they include, which is why many focus only on strong RCTs. Authors of these studies do their best to make sure the data are similar enough to pool together. These studies can be influential because they combine lots of data and information, painting a clearer picture of the effectiveness of therapies like PRP.

Retrospective Studies and Case Series/Reports

Briefly, these studies look at outcomes that have happened in the past and may look at large groups or small numbers of people. For example, a researcher could look at medical records from 2010-2015 to see the percentage of people who got PRP injections for shoulder pain, and report on how much pain relief or functional improvement people received based on what is written in past records. However, the quality of evidence from these studies is generally low, and there is a high risk of bias.  

What Are Some of the Most New and Essential Studies Surrounding PRP?

The research behind PRP is accelerating and improving at a steady pace. With each passing year, more high-quality studies with designs such as RCTs, prospective cohort trials, and systematic reviews/meta-analyses are coming out. Let’s talk about some studies that have come out in recent years that are relevant to common complaints we see here at Desert Spine and Sports Physicians.  

Knee Osteoarthritis

A 2021 RCT by Park et al. published in the Journal of the American Journal of Sports Medicine studied 110 people with knee osteoarthritis. Half were randomly assigned to receive a PRP injection into the knee joint, and the other half received hyaluronic acid for comparison to see which group did better after the injection. Both hyaluronic acid and PRP injections are offered here at Desert Spine and Sports Physicians. Because this was an RCT design, the researchers carefully measured each person’s age, severity of arthritis, and many other factors, including blood signaling molecule levels, to ensure the groups were equal. Each person in the study was followed at the same time intervals from the time of injection up to 6 months later. The people in the PRP group showed significantly more improvement after six months in the International Knee Documentation Committee (IKDC) score, which measures both pain and the ability to do normal activities and hobbies in everyday life. Those in the PRP group also did better than the hyaluronic acid group, which had various other secondary pain/function indexes. This type of study is considered a Level I, or highest quality, piece of evidence.

Another RCT of 87 people with knee osteoarthritis by Lin et al. used three randomized groups instead of two, comparing PRP versus saline (salt water) versus hyaluronic acid. This study found that PRP achieved a clinically significant difference in knee pain and function at all time points to 12 months using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, compared to the saline and hyaluronic acid groups.

Lateral Epicondylitis (Tennis Elbow)

An August 2024 study by Xu et al., also published in the American Journal of Sports Medicine, is a good example of a systematic review and meta-analysis using other studies’ data. Xu et al. conducted this study to see if PRP or corticosteroid injections for tennis elbow had better long-term outcomes (greater than 6 months out). In this study, researchers looked at all prospective studies about this topic in the past twenty years and found 11 different RCTs, including 730 people diagnosed with tennis elbow. The researchers combined all the data from each study and analyzed it together. Like the prior study, many pain and function scales, such as the Visual Analog Scale (VAS) for pain, were used to measure pain. Overall, those with tennis elbow who received PRP showed significantly better pain relief in the VAS pain score and two other functional scores after 6 months, while steroids had better short-term results at 2 months post-injection. This study is considered a Level II, or high-quality, evidence.

Similar studies, such as Chen et al. in 2021 and Tang et al. in 2020 have also shown improvements with PRP over steroids using a similar meta-analysis method using results from many previous studies.

Rotator Cuff Disease

For painful shoulders due to rotator cuff injury, a 2023 meta-analysis by Pang et al. compared PRP to steroid injections using information from 13 different RCTs in the past three decades, all of which were Level I or II evidence, including over 700 people total. The researchers made sure to study not only the relevant pain and function scales for shoulder pain but also things real-world patients care about, like how well someone can move their shoulder (i.e., range of motion). This study found that those with painful rotator cuff disease who received PRP hurt more and had less shoulder range of motion for the first month or so (which is an expected and normal result of a PRP injection) compared to a steroid injection. Still, in the medium and long-term (2-6+ months) after injections, the PRP group started to receive clinically significant improvements in pain and function over the steroid group.

This year, a 2024 RCT by Rossi et al. published in the Journal of Shoulder and Elbow Surgery studied 100 people with painful shoulders due to rotator cuff disease seen on shoulder MRI. Fifty of those 100 people were randomly selected to get a PRP injection into the shoulder, and the other fifty received a steroid injection. A year later, people who received PRP injections did significantly better from VAS pain and three other functional scales, as compared to the steroid group. Also, more people who received one steroid injection for rotator cuff pain tended to have a higher treatment failure rate (~30%) than those who got PRP (~12%), defined as pain lasting longer than three months requiring a second injection.

Greater Trochanteric Pain Syndrome (GTPS)

GTPS is a common cause of pain outside the hip, often involving tendons of the gluteus medius and minimus muscles that attach to the greater trochanter of the femur. A 2021 meta-analysis by Migliorini et al. published in the British Medical Bulletin included seven RCTs of Level I or II evidence, of which three directly compared PRP to steroid injections for treating GTPS. The studies used the visual analog pain scale (VAS) and the Harris Hip Score (HHS; a pain and functional score for hips) as their primary outcomes. This meta-analysis only used the HHS and VAS scores at the final follow-up appointments up to two years after injections.

Interestingly, this study did not find much difference in VAS pain between the steroid and PRP groups, but those who received PRP had significantly better function scores two years after the injection.

At Desert Spine and Sports Physicians, we stay current on the most recent advances in medical treatments to provide you with the best care. Countless other studies about PRP are not listed above, and while only some studies are always in agreement, what matters is that medical evidence continues to accumulate regarding PRP’s usefulness. 

This information provides a behind-the-scenes glimpse of continuing medical education’s role in our everyday visits with patients in our clinics. For those who wish to know more about platelet-rich plasma, please find answers to common questions about PRP here. 

Citations 

1. Park YB, Kim JH, Ha CW, Lee DH. Clinical Efficacy of Platelet-Rich Plasma Injection and Its Association With Growth Factors in the Treatment of Mild to Moderate Knee Osteoarthritis: A Randomized Double-Blind Controlled Clinical Trial As Compared With Hyaluronic Acid. Am J Sports Med. 2021 Feb;49(2):487-496. Doi: 10.1177/0363546520986867. PMID: 33523756. 
2. 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. PMID: 30611335. 
3. Xu Y, Li T, Wang L, Yao L, Li J, Tang X. Platelet-Rich Plasma Has Better Results for Long-term Functional Improvement and Pain Relief for Lateral Epicondylitis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Am J Sports Med. 2024 Aug;52(10):2646-2656. doi: 10.1177/03635465231213087. Epub 2024 Feb 15. PMID: 38357713. 
4. Chen XT, Fang W, Jones IA, Heckmann ND, Park C, Vangsness CT Jr. The Efficacy of Platelet-Rich Plasma for Improving Pain and Function in Lateral Epicondylitis: A Systematic Review and Meta-analysis with Risk-of-Bias Assessment. Arthroscopy. 2021 Sep;37(9):2937-2952. doi: 10.1016/j.arthro.2021.04.061. Epub 2021 May 5. PMID: 33964386. 
5. Tang S, Wang X, Wu P, Wu P, Yang J, Du Z, Liu S, Wei F. Platelet-Rich Plasma Vs. Autologous Blood Vs. Corticosteroid Injections in the Treatment of Lateral Epicondylitis: A Systematic Review, Pairwise, and Network Meta-Analysis of Randomized Controlled Trials. PM R. 2020 Apr;12(4):397-409. doi: 10.1002/pmrj.12287. Epub 2020 Jan 13. PMID: 31736257; PMCID: PMC7187193. 
6. Pang L, Xu Y, Li T, Li Y, Zhu J, Tang X. Platelet-rich plasma Injection Can Be a Viable Alternative to Corticosteroid Injection for Conservative Treatment of Rotator Cuff Disease: A Meta-analysis of Randomized Controlled Trials. Arthroscopy. 2023 Feb;39(2):402-421.e1. doi: 10.1016/j.arthro.2022.06.022. Epub 2022 Jul 8. PMID: 35810976. 
7. Rossi LA, Brandariz R, Gorodischer T, Camino P, Piuzzi N, Tanoira I, Ranalletta M. Subacromial injection of platelet-rich plasma provides greater improvement in pain and functional outcomes compared to corticosteroids at 1-year follow-up: a double-blinded randomized controlled trial. J Shoulder Elbow Surg. 2024 Aug 3:S1058-2746(24)00544-5. doi: 10.1016/j.jse.2024.06.012. Epub ahead of print. PMID: 39098382. 
8. Migliorini F, Kader N, Eschweiler J, Tingart M, Maffulli N. Platelet-rich plasma versus steroids injections for greater trochanter pain syndrome: a systematic review and meta-analysis. Br Med Bull. 2021 Sep 10;139(1):86-99. doi: 10.1093/bmb/ldab018. PMID: 34405857.