PRP (Platelet Rich Plasma) has become a very popular treatment for a multitude of orthopedic conditions.
The theory behind PRP is that our blood contains a lot more than red blood cells. Our blood is red because of these red-blood-cells, which contain iron (which is red), and the iron allows these cells to hold onto oxygen and transport oxygen throughout our body. However, our blood also contains platelets (which form clots to stop bleeding), stem cells, growth factors, and other proteins that enhance healing. Platelets not only stop bleeding by forming clots, they also release many biologically active molecules which target cells to regulate inflammation and promote healing. If we can isolate these pro-healing molecules, then we may be able to speed up healing by injecting these molecules around areas of injury.
At the same time, we do not want to inject red blood cells around areas of injury because they will not help with healing, and they will actually cause bruising, pain and inflammation. Therefore doctors have developed a way to "spin-down" our blood to separate out the red blood cells and the "plasma" which contains all of the platelets and pro-healing molecules. Once the plasma has been isloated, it can be injected.
That is the science, or "theory", behind PRP. Its common in medicine for things to make sense in a textbook, however they dont pan out to work in real life. This is commonly seen with cancer treatments, which seem to cure all cancers when performed on mice, but are less effective on humans. Similarly, looking at the effect of PRP on cartilage cells, it appears that it can promote cartilage restoration and reduce inflammation. In clinical studies, it appears to have some positive effects, but it is not clear how dramatically it will affect the course of a disease process such as arthritis.
A recent study compared standard gel-shot injections with PRP for the treatment of knee arthritis. There was no significant difference in pain scores after injection between the two medications (both medications were effective), however, there were some signs that the PRP decreased inflammation in the knee more than gel-shot injections.
The biggest problem is that PRP is being used to treat a wide variety of conditions and its expensive and difficult to create studies that compare the standard treatment with PRP to determine whether one is better than the other. PRP does show signs of promise, and hopefully it will prove to be a good treatment going forward.
References.
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 Cole BJ et al. Am J Sports Med. (2017)
Treatment with platelet-rich plasma is more effective than placebo for knee osteoarthritis: a prospective, double-blind, randomized trial. Patel S1, Dhillon MS, Aggarwal S, Marwaha N, Jain A. Am J Sports Med. 2013 Feb;41(2):356-64. doi: 10.1177/0363546512471299. Epub 2013 Jan 8. Better than placebo for 6 months.
The anti-inflammatory and matrix restorative mechanisms of platelet-rich plasma in osteoarthritis. Cole BJ, Karas V, Della Valle C, Tetreault MW, Mohammed HO, Fortier LA. Am J Sports Med. 2014 Jan;42(1):35-41. doi: 10.1177/0363546513507766. Epub 2013 Nov 5. laboratory study looking at expression of markers for inflammation. result was decrease expression in MMP, TNF alpha etc.
Platelet-rich plasma: why intra-articular? A systematic review of preclinical studies and clinical evidence on PRP for joint degeneration. Filardo G1, Kon E, Roffi A, Di Matteo B, Merli ML, Marcacci M. Knee Surg Sports Traumatol Arthrosc. 2015 Sep;23(9):2459-74. doi: 10.1007/s00167-013-2743-1. Epub 2013 Nov 26.