Introduction
Osteoarthritis (OA) is a disease which causes degeneration of joint tissue due to trauma, aging, and metabolic changes. The rising prevalence of knee OA has put an increasingly large physical and financial burden on the U.S. population. Traditional treatment options for OA include lifestyle modifications, pain management, physical therapy, and injections such as hyaluronic acid (HA), corticosteroids, or prolotherapy, with joint replacement as an option for those who have failed conservative measures. More recently, platelet-rich plasma (PRP) injections have started to gain traction in research and clinical practice. The authors of the review article The Use of Platelet-Rich Plasma in Symptomatic Knee OA summarize the current research and offer suggestions for future studies.
What is PRP and How Does It Work?
PRP is plasma that contains three- to five-times more platelets than whole blood, which typically has 150,000 to 300,000 platelets per microliter. The platelets in PRP contain numerous proteins which are involved in the initiation of healing and growth of new cells. With more proteins in the joint space, the progression of OA may potentially be slowed or halted. PRP is created by taking venous blood from the patient, centrifuging it, and injecting it into the joint space.
PRP vs Control Group
In one double-blind randomized control trial (RCT), 30 patients with knee OA who failed at least 6 weeks of nonoperative treatment received weekly intra-articular injections for either PRP or saline (control group) and were evaluated at one year. The PRP group showed statistically significant improvements in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) functional scale than those in the saline group.
PRP vs HA Injection
There were a few studies which compared PRP injections with HA injections. The first study looked at patients who received either two PRP injections at 4-week intervals or three HA injections at one-week intervals, the standard for this injection. At 12 months, pain scores improved significantly more in the PRP group and only in the PRP group was there improvement on the WOMAC and Study 36-Item Short Form Health Survey (SF-36) functional questionnaires.
A second study reported similar improvements between PRP injection and HA injections at a two-month follow-up but PRP results were better than HA at the 6-month follow up, especially in younger patients, which suggests a longer-term benefit for PRP. When comparing patient age and the degree of OA, the study reported PRP and HA showed similar results in patients over 50 and in those with more advanced OA, suggesting PRP might have better outcomes than HA in younger patients with either cartilage lesions or early OA.
A third double blind randomized control trial compared PRP to HA using the WOMAC, International Knee Documentation Committee (IKDC) for overall function, and Visual Analog Scale (VAS) for pain. No difference was seen between groups in regard to WOMAC score, but there was significant improvement in the IKDC score and VAS score in the PRP group.
PRP vs. Corticosteroid Injection
In a study comparing PRP to corticosteroid injections, PRP provided superior pain and symptom relief for patients with OA as well as significantly improved quality of life when compared to those receiving a cortisone injection.
PRP vs. Prolotherapy
When compared to prolotherapy in a double-blind randomized control trial, PRP injections were more effective in improving WOMAC scores at 1 month, 2 months, and 6 months post-injection.
Limitations
The largest limitations thus far in PRP research is the lack of consistency among PRP processing and concentrations which makes it difficult to prepare an ideal clinical PRP solution. There are still only a few randomized control trials that look at long-term follow-up; more research is needed in this area. The high cost and lack of insurance coverage for PRP injections (out-of-pocket costs range from $500 to $2,000 per injection) limit the number of people who can afford PRP and thus limits the real-world evidence that can be gathered.
Conclusion and PTF Implications
There is clear evidence to support the use of PRP in knee OA. The main advantages of using PRP are its longer-lasting and more efficacious function in restoring articular function when compared with HA injections, corticosteroid injections, and prolotherapy. It appears that PRP is most beneficial for early/low-grade OA compared with more advanced OA. Better outcomes are seen in patient populations under 50 years old with earlier OA due to PRP preventing or slowing the progression of the disease. As research increases on this subject, the use of PRP to treat OA will potentially increase leading to a possible decrease in total joint replacements and financial expenditures associated with OA. A combination of PRP injections and a tailored PT program could prove beneficial for patients with early knee OA and prevent the need for total joint replacement.
Reference
Southworth, T., Naveen, N., Tauro, T., Leong, N., Cole, B. (2019). The Use of Platelet-Rich Plasma in Symptomatic Knee Osteoarthritis. The Journal of Knee Surgery. 32:37-45.