Platelet-Rich Plasma and Its Role in Knee Osteoarthritis Relief

Introduction to Knee Osteoarthritis and Its Treatment Options

Knee osteoarthritis (KOA) is a prevalent degenerative joint disease characterized by the progressive deterioration of articular cartilage, leading to pain, stiffness, and decreased mobility. This condition significantly impacts the quality of life of millions of individuals, especially the elderly, making it one of the leading causes of disability worldwide (Sharma & Solomon, 2021). Traditional treatment options for KOA include pharmacological approaches such as non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and analgesics, alongside non-pharmacological interventions like physical therapy and lifestyle modifications (D’Apuzzo et al., 2017). However, these treatments often provide only temporary relief and come with potential side effects, leading to an increasing interest in alternative therapies like platelet-rich plasma (PRP) injections.

PRP therapy has emerged as a promising treatment option for KOA due to its potential to enhance healing through the delivery of growth factors and cytokines that promote tissue repair and reduce inflammation (Khatab et al., 2018). The clinical efficacy of PRP in alleviating pain and improving function in KOA patients has garnered considerable attention, yet the underlying mechanisms remain to be fully elucidated.

Mechanism of Action: How Platelet-Rich Plasma Alleviates Pain

The analgesic effects of PRP in KOA are attributed to its ability to modulate inflammatory responses and promote tissue regeneration. PRP is derived from the patient’s own blood and contains a high concentration of platelets, which release various growth factors, including transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) (Boffa et al., 2021). These factors play crucial roles in the healing process by stimulating chondrocyte proliferation and enhancing collagen synthesis within the cartilage matrix.

Recent studies have demonstrated that PRP can effectively reduce inflammation by modulating macrophage activity in the synovial microenvironment. In particular, the polarization of macrophages from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype is a critical mechanism through which PRP exerts its therapeutic effects (Xu et al., 2025). The M1 macrophages release pro-inflammatory cytokines such as interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α), contributing to joint inflammation and pain, whereas M2 macrophages secrete anti-inflammatory cytokines, promoting tissue repair (Zhao et al., 2022).

Research indicates that PRP treatment can significantly decrease the ratio of M1 to M2 macrophages in the synovial tissue, thereby alleviating pain and reducing inflammation (Xu et al., 2025). Furthermore, PRP enhances the secretion of anti-inflammatory mediators like IL-10, which further aids in reducing pain and promoting healing within the joint.

The Impact of Macrophage Polarization on Osteoarthritis

Macrophage polarization plays a pivotal role in the pathogenesis of KOA. The balance between M1 and M2 macrophages in the joint microenvironment can dictate the extent of inflammation and pain experienced by patients. An increased presence of M1 macrophages is often associated with elevated levels of pro-inflammatory cytokines that exacerbate KOA symptoms. Conversely, a shift towards M2 macrophages, which are involved in tissue repair and regeneration, can mitigate these symptoms (Hsueh et al., 2020).

Studies have shown that interventions aimed at modulating macrophage polarization can significantly influence the progression of KOA. For instance, the use of PRP has been observed to shift macrophage populations towards the M2 phenotype, thereby decreasing the inflammatory response and consequent pain (Xu et al., 2025). This shift not only facilitates cartilage repair but also enhances the overall regenerative capabilities of the joint, offering a multifaceted approach to KOA management.

Clinical Evidence Supporting Platelet-Rich Plasma Efficacy

Numerous clinical trials have investigated the efficacy of PRP in the treatment of KOA, with many reporting positive outcomes. A systematic review indicated that PRP injections could lead to significant improvements in pain and functionality compared to placebo and traditional treatments (Cook & Smith, 2018). Intra-articular PRP administration has been associated with reduced levels of IL-1β and TNF-α in synovial fluid, indicating a decrease in inflammatory processes (Xu et al., 2025).

A meta-analysis of randomized controlled trials revealed that patients receiving PRP exhibited greater reductions in pain and improvements in functional scores, such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), compared to those treated with hyaluronic acid or saline (Nie et al., 2021). Furthermore, long-term follow-ups suggest that the analgesic effects of PRP may persist for up to 12 months post-treatment, highlighting its potential as a durable pain relief strategy (Boffa et al., 2021).

Table 1: Summary of Clinical Trials on PRP for KOA

Conclusion: Future Perspectives on Platelet-Rich Plasma in Osteoarthritis

The application of PRP in the treatment of knee osteoarthritis represents a significant advancement in pain management strategies. The ability of PRP to modulate macrophage polarization, reduce inflammation, and promote tissue regeneration underscores its therapeutic potential. As research continues to elucidate the mechanisms of action and optimize treatment protocols, PRP may become a cornerstone therapy in the management of KOA, offering patients a viable alternative to traditional treatments.

Future studies should focus on refining PRP preparation techniques, identifying patient populations that may benefit most from PRP therapy, and establishing standardized protocols for its clinical application. Additionally, exploring the synergistic effects of PRP with other therapeutic modalities may enhance treatment outcomes for individuals suffering from knee osteoarthritis.

FAQ

What is Platelet-Rich Plasma (PRP)?
PRP is an autologous concentration of platelets derived from a patient’s blood, containing growth factors and cytokines that promote healing and reduce inflammation.

How does PRP help in knee osteoarthritis?
PRP alleviates pain and inflammation by modulating macrophage polarization and promoting the regeneration of cartilage tissue within the knee joint.

Are there any risks associated with PRP therapy?
Since PRP is derived from the patient’s own blood, the risk of allergic reactions or disease transmission is minimal. However, potential side effects include pain at the injection site and temporary worsening of symptoms.

How long do the effects of PRP last?
Clinical studies suggest that the analgesic effects of PRP can last up to 12 months, with many patients experiencing significant improvements in pain and function.

Is PRP therapy covered by insurance?
Coverage for PRP therapy varies by insurance provider and policy. Patients should consult with their insurance company to determine coverage options.

References

1. Sharma, L., & Solomon, C. G. (2021). Osteoarthritis of the Knee. N. Engl. J. Med., 384, 51-59. doi:10.1056/NEJMcp1903768
2. D’Apuzzo, M., Westrich, G., Hidaka, C., Jung Pan, T., & Lyman, S. (2017). All-cause versus complication-specific readmission following total knee arthroplasty. J. Bone Joint Surg., 99, 1093-1103. doi:10.2106/jbjs.16.00874
3. Khatab, S., et al. (2018). Intra-articular injections of platelet-rich plasma releasate reduce pain and synovial inflammation in a mouse model of osteoarthritis. Am. J. Sports Med., 46, 977-986. doi:10.1177/0363546517750635
4. Boffa, A., et al. (2021). Platelet-rich plasma injections induce disease-modifying effects in the treatment of osteoarthritis in animal models. Knee Surg. Sports Traumatol. Arthrosc., 29, 4100-4121. doi:10.1007/s00167-021-06659-9
5. Xu, J., et al. (2025). Platelet-rich plasma relieves inflammation and pain by regulating M1/M2 macrophage polarization in knee osteoarthritis rats. Sci. Rep., 15, 9750. doi:10.1038/s41598-025-97501-6
6. Nie, L. Y., Zhao, K., Ruan, J. Q., & Xue, J. (2021). Effectiveness of platelet-rich plasma in the treatment of knee osteoarthritis: A meta-analysis of randomized controlled clinical trials. Orthop. J. Sports Med., 9, 11. doi:10.1177/2325967120973284