PRP for the Management of Osteoarthritis of the Knee
What is Platelet Rich Plasma (PRP)?
Blood is primarily composed of red blood cells, white blood cells and platelets carried by a liquid called plasma. The primary responsibility of platelets is to help blood to clot. Platelets also contain several important proteins including growth factors which can help to promote tissue healing and cytokines which signal different cellular functions.
Platelet rich plasma (PRP) is made by taking a sample of the patient’s blood and spinning it in a centrifuge. This separates the platelets from other blood cells. When combined with plasma, the PRP mixture that results has a five to ten-fold increased concentration of platelets. The process can be done in the office setting and takes approximately 10-15 minutes. The PRP can then be injected back into the body at various sites. The theory is that this high concentration of growth factors and other chemicals can contribute to tissue healing and subsequent pain relief.
What conditions can PRP treat?
Scientists and clinicians are still learning what conditions PRP can be used to treat. At this time, there have been mixed results. Some studies show that PRP is helpful, and others demonstrate no improvement when compared with placebo. Even though studies are inconclusive, there is a growing market and interest in using PRP injections to treat muscle, tendon and joint pain.
Some of the successful applications of PRP injections have been in treating damage to tendons such as lateral epicondylitis (tennis elbow), plantar fasciitis and Achilles tendinosis. There have been some studies examining the use of PRP for the treatment of osteoarthritis of the knee.
What have studies shown?
A 2016 paper combined the results of ten prior studies where PRP was used for the treatment of osteoarthritis of the knee¹. The study involved over 1,000 patients who were included in prospective, randomized trials. Compared with injections of saline as the placebo, patients injected with PRP experienced better pain relief and functional improvement up to one year following the injection. When compared with injections of hyaluronic acid (HA – a commonly given injection for arthritis), PRP had small but real improvements in pain relief a year after the injections.
In another randomized study, scientists compared injections of PRP, HA or the combination of PRP and HA². The findings showed that the patients who received the combination of PRP and HA had better pain relief and functional improvements. These results were measured and found to be significant from one to three months after the injection.
It is important to emphasize that these studies primarily focused on patients with mild to moderate osteoarthritis of the knee, and that there is no data suggesting that the injections slowed the progression of the arthritis or helped to grow new cartilage.
What are the downsides to PRP injections?
There appear to be few complications from injections of PRP. Like all injections, patients may experience injection site pain and a low risk of infection. While there is some concern for injecting high concentrations of any chemical – including growth factors and cytokines – PRP injections appear to be reasonably well tolerated.
Perhaps the biggest downside to PRP injections is the cost. Most of these injections are not covered by insurance, and the cost of a single injection can be up to $1,000. With the inconsistent results that have been demonstrated to date, most surgeons and medical societies have not recommended PRP as part of the routine care for osteoarthritis.
The results of using PRP injections to treat osteoarthritis are mixed; yet it remains an attractive treatment alternative. Many questions remain that will hopefully be answered in future studies. Patients should recognize the current unknowns about PRP treatment and focus on the first line treatments for osteoarthritis such as weight loss, exercise and anti-inflammatory medications as recommended by their doctors.