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How does PRP help with healing?

Platelet rich plasma (PRP) is a new type of injection treatment that we’ve introduced at The Physios because it provides excellent results for certain conditions that can sometimes prove difficult to fix with other physiotherapy or injection treatments. PRP is branch of regenerative medicine which seeks to restore, repair and regenerate diseased tissues and, in the field of musculoskeletal medicine, has been shown to be particularly helpful in treating joint (e.g. knee arthritis) and tendon problems (e.g. tennis elbow). PRP is used to help the healing of injured or dysfunctional tissues in order to improve the quality of life and avoid or delay the need for invasive intervention (like orthopaedic surgery).

“So how does PRP work exactly?” asked a colleague. I did my best to answer them over our lunch break but then realised this was going to be the question everyone asked. So this blog is going to get a little geeky as I dust off my old biochemistry hat to present on how PRP helps with healing.

What are plasma and platelets?

Plasma makes up around 55% of the blood in your body where it acts as a medium to suspend the blood cells (red and white). Plasma also helps to suspend other important proteins for transport around the body such as proteins for healing (platelets) and signal proteins called hormones.

Platelets (also called thrombocytes) are essential for blood clotting and healing such as when you cut your finger. Thrombocytes kick-start the healing process by releasing granules which are full of the essential building blocks for healing – generally called bioactive molecules. Amazingly, plasma contains over 1500 bioactive proteins which mastermind tissue repair and wound healing – among these are growth factors and cytokines. The biochemistry of healing is fascinating but immensely complex, especially if we start to consider how each individual growth factor is involved in the process. For now, let’s agree that platelets/thrombocytes are important for injured tissues and the proteins secreted by platelets (bioactive molecules) do incredible things to heal the body.

What is platelet rich plasma?

PRP is a preparation of plasma which is rich in platelets and bioactive proteins. This is produced by taking a sample of blood from the patient and separating its constituent parts by a process of centrifugation. As we discussed earlier, there are different cells and proteins that make up your blood. These different components are different sizes and different weights. Platelets are the smallest type of blood cell (about 20 times smaller than red blood cells) and the bioactive proteins that they produce are smaller still. When we centrifuge blood, the heaviest components (red blood cells and white blood cells) settle at the bottom of the tube and the lighter components (platelets and bioactive proteins) remain at the top.

This process is important as not all the components of blood are helpful in the healing process. Red blood cells can be toxic to cells as they degrade and neutrophils (a type of white cell) encourages inflammation and delays the healing process. By taking a small volume of blood and separating it out, we are left with a concentrated portion of plasma – rich in all the essential components of healing.

So how does PRP help with healing?

In different tissues, including the musculoskeletal system, the healing process can take a long time. The healing process is even more limited when there is limited blood supply and slow cell turnover. The use of PRP can help with healing by speeding up the neovascularization (increasing the blood supply). It also provides the components necessary for cell regeneration in damaged tissue. Also, by increasing the blood supply, PRP stimulates the requirement, proliferation and differentiation of the cells, which are involved in the healing process. Lets look for a moment at joint arthritis and tendon problems – two of the main indications for PRP injections in the musculoskeletal system:

Joint arthritis

The specific example here is knee osteoarthritis but the same rationale can be applied to all articular cartilage. Knee OA in its early and moderate stages is not primarily a problem with the bones, it is due to a loss and breakdown of the cartilage that covers the bones. Adult articular cartridge has a poor ability to regenerate and limited potential for healing as it is avascular and aneural (poor blood and nerve supply). Essentially tissues cannot heal without a good blood supply. To date all treatments for OA seek to treat the symptoms and slow the progression. By injecting all the components involved in the healing process, PRP can help with healing the articular cartilage and combat the arthritic process. Given the rationale presented, arguably the earlier we can administer PRP in the degenerative process the better.

Tendon injury

Similarly to articular cartilage, tendons are dense connective tissue with a poor blood supply. Common tendon injuries include the Achilles tendon, jumpers knee, tennis & golfers elbow and injuries the the rotator cuff. Chronic tendon injuries (tendinopathy) is characterised by a dysfunctional and prolonged inflammatory (swelling) cascade and a failed healing process resulting in weakened tissue, full of scar tissue. This results in pain, weakness and a failure to return to functional loading/sport. We may not offer an injection initially as a non-invasive treatment like Shockwave Therapy has great outcomes in tendinopathy. However PRP injections (especially growth factors) have been shown to enable a competent inflammatory cascade. PRP also enables the synthesis of collagen and in particular type III collagen which is responsible for spring and elasticity of tendons.

PRP – a fresh approach to healing

Because PRP is a from of regenerative medicine, we need to view its application in clinical practice quite differently to other interventions such as cortisone injections or joint replacements. The emphasis with regenerative medicine is to provide an environment where healing of degenerative or recalcitrant conditions occurs. This constitutes an exciting and significant breakthrough in our field and allows us to provide effective therapy for many conditions that proved difficult to treat previously.

Let’s go back to the treatment of knee OA – it is not so long ago that the only effective treatment available to control symptoms was a cortisone injection (sometimes anti-inflammatory medication helped too). The problem with cortisone injections was the possible deleterious effects of the cortisone on joint surfaces if injections were repeated too frequently. The treatment therefore had to be used very sparingly. Cortisone injections remain a recognised and useful treatment in some cases but it is important to recognise that other therapies like PRP and HA offer effective alternatives. As a degenerative condition, knee OA ultimately led to surgery in many cases to ‘remove’ the damaged tissue (knee replacement) which alleviated the symptoms and reduced the disability. That said, joint replacement surgery provides an outstanding treatment for the more severely affected arthritic knees.

PRP now enables us to use injection therapy to actively treat conditions that previously proved tricky either due to the limited healing capacity of the tissue or the absence of a proactive alternative.

* The author of this blog, Johnny Cassidy, studied Biochemistry at Sheffield University before embarking on a career in physiotherapy. It would be fair to say he knows a lot more about physiotherapy than biochemistry but enjoyed the chance to blend his knowledge to make this (hopefully!) an informative blog.