Knee Injections (Part 3) – Platelet Rich Plasma (PRP)

PRP (Platelet Rich Plasma) can be considered as the “new kid on the block”. PRP injections into the knee have only started to become popular over recent years.

PRP is a biological treatment where a concentrated dose of endogenous (produced by the patient’s body) growth factors are injected into the area of injury to aid in repair. Its use has been fairly common and accepted in certain dental and orthopaedic conditions. In addition, some doctors have also used it for dermatological conditions and aesthetic purposes.

"...a concentrated dose of endogenous (produced by the patient’s body) growth factors are injected into the area of injury to aid in repair."

PRP basically refer to plasma that contains platelets at a higher concentration than the baseline blood concentration. The concentrated platelets then release the growth factors which are used for the therapeutic purposes.

PRP is derived from blood drawn from the patient. This blood is then centrifuged (put in a special machine and spun quickly) to separate the blood components into different layers. The layer of fluid containing the platelets is then removed and further processed or used immediately as an injection. There is currently no industrial standard in the method of preparing PRP and hence some investigators find it difficult to draw conclusion from the results of the different studies.

To make matters more confusing, each injection may differ in concentration of growth factors as they are derived from different patients. In fact, studies have shown that the concentration of growth factors in PRP drawn from the same patient, may vary as a result of the activity that the patient had participated in prior to the blood withdrawal.

Even though there are so many confounding issues surrounding the preparation and use of PRP, there have also been many studies that have shown improvement in clinical symptoms when PRP is injected into the knee to treat osteoarthritic knee pain. These studies have been criticized by some as having design flaws in them. As such, the current AAOS clinical practice guidelines pertaining to it’s use in osteoarthritis gives the recommendation of “inconclusive”. This means that the conclusion of whether this therapy works has not been proven by strongly designed studies yet.

"...the concentration of growth factors in PRP drawn from the same patient, may vary as a result of the activity that the patient had participated in prior to the blood withdrawal."

Currently, there are many doctors around the world who use this modality to treat knee pain in patients with osteoarthritis. Advantages of PRP are that the products introduced into the knee come from the patients’ themselves and hence there is no issue with allergy or rejection. Furthermore, several studies have shown positive effects in clinical relief of knee pain. PRP is also simple to prepare and can be administered in the doctors consult room. 

Disadvantages include the lack of strong literature evidence to prove that PRP injections clearly help in relieving osteoarthritis knee pain and also the lack of standardisation in preparation and administration of the injection. With more well-designed studies being currently conducted, it is hoped that more evidence will present itself in the near future.

Conclusion

Knee injections are a quick and useful modality in treating knee pain resulting from degeneration or cartilage damage in the knee. If you experience knee pain and find that physiotherapy and oral analgesia do not seem to relieve the symptoms, you should discuss this option with your doctor to see if it is suitable for you.

About the Author
Dr Sean Leo is a former SAF Medical Scholarship recipient and served as CO of the Medical Classification Centre at CMPB. After retiring from active military service in 2012, Dr Leo joined Changi General Hospital where he was the Director of Hip and Knee Service.  He subsequently went into private practice at Mt Elizabeth Novena Hospital. As an orthopaedic surgeon, Dr Leo is specialised in knee and lower limb surgery with a focus on sport injuries, rehabilitation and performance. 

For an appointment, email appointment@orthokinetics.sg.