Updated: Apr 22
PRP stands for platelet rich plasma. These types of injections have gained popularity over the last few years as a treatment option for a variety of musculoskeletal injuries / conditions including tendinopathies, muscle injuries and osteoarthritis. In this article I’ll discuss how these injections work, what factors may affect how well they work and also what the research is showing with regards to what conditions they may be useful for.
In this article:
I've also discussed it in this video
How they prepare the PRP solution
They prepare the platelet rich plasma solution from your own blood. The blood is drawn and then spun at a high speed. By spinning it, you can separate the blood into it’s different parts. The layer of plasma that contains a high concentration of platelets is then drawn off and injected into the injury site.
Why PRP injections are used
Why do they do these injections? Platelets release lots of bioactive substances which include pro- and anti-inflammatory mediators as well as a variety of growth factors. Studies on animals have shown that through releasing these substances, high concentrations of platelets can decrease pain and stimulate healing – especially collagen growth.
In short, they use PRP injections in the hope that it will kick-start the healing process for injuries where healing is slow or not really happening like for instance in tendinopathies and osteoarthritis.
You may notice that I say “in the hope” that it will help – this is because things are never quite as simple and there appear to be quite a lot of factors that can affect how well PRP works.
Factors that may affect how well they work
How they prepare the PRP solution can cause a large variation in how many platelets the solution contains and also how well the platelets release their bioactive substances (like growth factors). It’s no use having a large number of platelets, but they’re not willing to release the stuff that are needed to get the healing process going.
There are currently more than 16 types of machines available that can be used to prepare the PRP and they have all been shown to produce different concentrations of platelets. Some clinicians spin the solution once and others twice. There are also a variety of different substances that they can mix into the PRP to stimulate the platelets to release their bioactive substances. At this point in time, researchers don’t actually know what preparation method is the best.
The interesting thing is that the PRP solution can also vary on different days, even if it is prepared in exactly the same way for the same patient. This is because the patient’s own health and nutrition can affect how many platelets they have in their blood, the quality of their platelets and how readily the platelets will release their growth factor and other substances.
The following lifestyle factors have been shown to influence platelet quality and function in patients:
Mental stress (like public speaking or doing a maths exam) and physical stress (like exercise) have been shown to cause platelets to release their bioactive substances. This means that if you’re subjected to either mental or physical stress before your blood is drawn, your platelets may already be depleted and won’t have much left to give to your injury site.
Diets that are high in saturated fats, sugar, simple carbohydrates or that contain caffeine, quercetin (a flavonoid present in high levels in onions, apples, tea and wine) and isoflavones (present in chickpeas and soybeans) can affect your platelets.
Alcohol and smoking aren't good
Certain drugs can also affect your platelets of which the most commonly used include NSAIDS, antihistamines and antibiotics.
If you're due to have a PRP injection, you may want to see if you can manage your stress and diet during the week leading up to your injection.
What conditions do PRP injections work for?
With all these factors capable of affecting the PRP solution's quality and effectivity, it’s no wonder that the current research is showing quite a lot of conflicting results. According to the most recent research, PRP appears to be a useful adjunct to treatment for the following conditions (Reference 1, Reference 2, Reference 3):
Rotator Cuff Tendinopathy;
Donor site pain in Anterior Cruciate Ligament (ACL) reconstruction with Patellar Tendon Autograft;
High Ankle Sprains.
Acute fracture or non-union
Surgical augmentation with PRP in Rotator Cuff Repair, Achilles Tendon Repair and ACL reconstruction.
When should you consider having a PRP injection?
PRP is by no means a magic cure and I think this is partly down to the fact that we just don’t yet know how to prepare the best possible PRP solution with the most active platelets. I suspect that PRP procedures will still improve a lot over the next few years and may even become useful for conditions like Achilles tendinopathy.
Currently I would advise patients to first try at least 12 weeks of a progressive rehab programme before they consider any other interventions. Rehab exercises have been shown to be very effective for the treatment of tendinopathies etc., but it has to be tailored to your specific injury and your specific ability. Doing the same exercises at the same level for 12 weeks does not count as rehab!
How we can help
Need more help with your injury? You’re welcome to consult one of the team at SIP online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine. But at Sports Injury Physio we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.
About the Author
Lin, M.-T., et al. (2018). "Meta-analysis comparing autologous blood-derived products (including platelet-rich plasma) injection versus placebo in patients with Achilles tendinopathy." Arthroscopy: The Journal of Arthroscopic & Related Surgery 34(6): 1966-1975. e1965.