Nov 2111 min read

PRP Injections for Knees: A Breakthrough Treatment for Knee Pain and Injury Recovery

Knee pain, a common issue affecting millions of individuals worldwide, often stems from both acute injuries and chronic conditions like osteoarthritis. Treatment options for knee pain range from conservative methods, such as physical therapy and anti-inflammatory medications, to more invasive interventions, including surgical procedures.

In recent years, however, there has been a growing interest in innovative, minimally invasive therapies that harness the body’s natural healing capabilities. One such therapy is platelet-rich plasma (PRP).

PRP is gaining recognition not only for its application in knee osteoarthritis but also for its effectiveness in managing chronic tendon injuries, ligament tears, and other joint-related issues. This article explores the use of PRP injections for knees, emphasizing its role in managing knee osteoarthritis, sports injuries, and joint degeneration.

What is PRP, and How Does It Work?

Understanding Platelet-Rich Plasma (PRP)

Platelet-rich plasma (PRP) is an autologous biological product derived from whole blood, where platelets are concentrated above baseline levels. In a standard blood sample, platelets typically make up about 6% of the total volume. However, in PRP, this concentration is significantly higher, typically ranging from 2 to 10 times the baseline.[1] These platelets are rich in growth factors and cytokines, which play a crucial role in tissue healing and repair.

Upon activation, platelets release various growth factors, including platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor-beta (TGF-β), and insulin-like growth factor (IGF). These growth factors stimulate several biological processes that are critical to tissue repair, including cellular proliferation, differentiation, migration, and angiogenesis.[2]

In addition to these growth factors, PRP also contains bioactive proteins that modulate the inflammatory response and promote the regeneration of damaged tissues. This is particularly useful in conditions like PRP for plantar fasciitis, where chronic inflammation impedes healing[3], and in PRP for rotator cuff tears, where tendon repair is a slow process due to limited blood supply to the tendon tissue.[4]

How PRP Affects the Knee Joint

The knee joint is a complex structure composed of bones, cartilage, tendons, ligaments, and synovial fluid. In conditions such as knee osteoarthritis, the protective cartilage that cushions the bones wears down, leading to pain, stiffness, and reduced joint function. PRP works by creating an enhanced healing environment within the joint. The growth factors in PRP stimulate local cells, including chondrocytes, tenocytes, and synoviocytes, promoting the repair of damaged tissues.[5]

For instance, PRP for meniscus tears has shown potential in accelerating the healing of the meniscus, a structure within the knee that is particularly prone to injury. The meniscus has poor vascularization, especially in its inner regions, making it difficult to heal naturally. By enhancing angiogenesis and stimulating the recruitment of reparative cells, PRP helps in repairing meniscal tissue and improving overall knee function.[6]

In the case of osteoarthritis, PRP has been shown to influence the behavior of synoviocytes. These cells are responsible for producing synovial fluid, which lubricates the joint and reduces friction between the cartilage surfaces.[7] PRP's growth factors also inhibit the activity of catabolic enzymes, such as matrix metalloproteinases (MMPs), which degrade cartilage and exacerbate the progression of osteoarthritis. In this way, PRP can slow the degenerative process and promote joint homeostasis.[8]

PRP vs. Traditional Knee Treatments

Comparing PRP to Common Treatments

Traditionally, patients suffering from knee pain due to osteoarthritis or injury have been treated with non-surgical interventions such as corticosteroid injections, hyaluronic acid injections, and oral non-steroidal anti-inflammatory drugs (NSAIDs). While these treatments can provide temporary relief, they do not address the underlying causes of tissue damage or degeneration. Moreover, repeated use of corticosteroids has been associated with adverse effects, including the weakening of cartilage and soft tissues over time.[9]

In comparison, PRP offers a biological approach to healing by directly stimulating the body’s own reparative processes. While corticosteroids reduce inflammation in the short term, PRP encourages tissue growth and long-term healing.

PRP vs. stem cells has also been an area of debate in recent years. While stem cell therapy holds promise for tissue regeneration by differentiating into cartilage, tendon, or ligament cells, PRP offers a less invasive, more cost-effective, and quicker solution. Stem cell procedures often require harvesting cells from the bone marrow or adipose tissue, followed by complex processing. PRP, on the other hand, can be prepared in-office from a simple blood draw and does not require extensive manipulation, making it a more accessible option for many patients.[10]

Advantages of PRP for Knee Pain and Function

One of the most compelling reasons for choosing PRP over traditional treatments is its ability to improve both pain and joint function. PRP has been shown to reduce knee pain by modulating the inflammatory response and promoting tissue healing.[11] This dual action results in not only symptom relief but also functional improvement. Patients treated with PRP report greater ease in performing daily activities, increased range of motion, and a decrease in the need for pain medications.

Another significant advantage of PRP is its ability to slow the progression of degenerative conditions like osteoarthritis. By enhancing the biological processes that maintain cartilage health and joint function, PRP helps to preserve joint integrity and prevent further deterioration. [12] This is especially important in patients who are not ready for surgical interventions like knee replacement or those looking to avoid surgery altogether.

Common Applications of PRP Injections for Knee Pain

Treating Knee Osteoarthritis with PRP

Knee osteoarthritis (OA) is a leading cause of disability worldwide, particularly among older adults. It is characterized by the gradual breakdown of cartilage, leading to joint pain, stiffness, and loss of function. Conventional treatments for knee OA often focus on symptomatic relief rather than addressing the underlying degeneration. PRP, however, offers a promising solution by targeting the degenerative process itself.[13]

Several studies have demonstrated that PRP injections can significantly reduce pain and improve joint function in patients with knee OA. PRP’s ability to stimulate the production of extracellular matrix proteins, such as collagen and proteoglycans, supports cartilage health and slows the degenerative changes seen in osteoarthritis. Additionally, PRP’s anti-inflammatory properties help to reduce synovial inflammation, which is a significant contributor to the pain and stiffness associated with knee OA.[5], [7], [11], [12], [14]

Patients with early to moderate knee OA tend to respond best to PRP, with many experiencing long-lasting improvements in pain and function. In advanced cases of OA, PRP can still offer symptomatic relief and may help delay the need for joint replacement surgery. However, PRP is not typically a cure for advanced OA and should be considered as part of a comprehensive treatment plan that includes physical therapy, weight management, and, in some cases, other medical interventions.

PRP for Sports-Related Knee Injuries

Knee injuries are common among athletes and active individuals, particularly those involved in sports that require sudden stops, turns, or impacts, such as soccer, basketball, and skiing. Common sports-related knee injuries include ligament tears (e.g., ACL and MCL tears), meniscal injuries, and patellar tendinopathy. PRP therapy has gained popularity in the sports medicine community due to its ability to accelerate healing and reduce recovery times without the need for invasive surgery.

In cases of ligament injuries, such as ACL tears, PRP can be injected into the damaged tissue to promote healing and tissue repair. The growth factors in PRP stimulate the proliferation of ligament cells, improving tissue integrity and strength.[15] For tendon injuries, such as patellar tendinopathy, PRP helps to repair damaged tendon fibers by promoting collagen synthesis and reducing inflammation. Athletes treated with PRP often report faster recovery times, allowing them to return to their sport sooner than with conventional treatments alone.[16]

In addition to treating acute injuries, PRP is also effective in managing chronic conditions that can result from repetitive stress and overuse. Conditions like plantar fasciitis, which is common in runners and athletes who put significant stress on their feet and lower legs, respond well to PRP therapy. PRP helps reduce the chronic inflammation associated with plantar fasciitis, facilitating tissue healing and reducing pain.3

How PRP Injections for Knees Work

The PRP Injection Process

The process begins with extracting a small amount of blood from the patient, typically between 20 and 60 mL, depending on the intended volume of PRP.

The blood is then placed into a centrifuge, where it undergoes a process of separation. The centrifugation process isolates the platelet-rich plasma from the red blood cells, white blood cells, and other plasma components. The resulting PRP concentrate contains a high concentration of platelets and growth factors, which are essential for tissue repair.

Once the PRP is prepared, it is injected directly into the affected knee joint using a sterile technique. The use of ultrasound guidance during the injection process ensures precise delivery to the area of damage, maximizing the therapeutic benefits.

Multiple PRP Injections for Optimal Results

While some patients experience significant improvements after a single PRP injection, multiple injections may be necessary to achieve optimal results. The typical protocol involves a series of two to three injections spaced several weeks apart. Each injection stimulates further healing, building upon the effects of the previous treatment.

Post-PRP Injection: Recovery and Results

Recovery Timeline and Patient Expectations

The recovery timeline following PRP injections varies from patient to patient. It depends on factors such as the severity of the condition being treated, the patient’s overall health, and adherence to post-injection care protocols. Generally, patients can expect mild discomfort at the injection site for a few days following the procedure. This discomfort is typically minimal and can be managed with over-the-counter pain medications, such as acetaminophen. It is essential to avoid NSAIDs, as these can interfere with the healing process facilitated by PRP.

Achieving Optimal Healing and Long-Term Benefits

Achieving the best outcomes with PRP therapy requires a comprehensive approach that includes proper post-treatment care and lifestyle modifications. For patients with knee osteoarthritis, maintaining a healthy weight and engaging in low-impact exercises, such as swimming or cycling, can help preserve joint function and reduce stress on the knees. A balanced diet rich in anti-inflammatory nutrients, such as omega-3 fatty acids, can further support joint health and enhance the healing process initiated by PRP. Additionally, patients with chronic conditions may require ongoing management to prevent re-injury and maintain optimal function.

Safety and Considerations for PRP Knee Injections

PRP Injection Safety Profile

PRP has an excellent safety profile, primarily because it is an autologous therapy, meaning it uses the patient’s own blood. This significantly reduces the risk of allergic reactions, immune responses, and infections that are more common with other injectable therapies. The preparation process is performed under sterile conditions, minimizing the risk of contamination.

Patients generally tolerate PRP injections well, and side effects are typically mild. The most common side effects include localized pain or irritation at the injection site, which usually resolves within a few days.

Risks and Side Effects to Consider

While PRP is considered safe, there are some risks and side effects to consider. In rare cases, patients may experience more significant discomfort, swelling, or bruising at the injection site. These side effects are typically self-limiting and do not require medical intervention. However, it is essential to monitor patients for any signs of infection or adverse reactions, particularly in those with compromised immune systems.

The Role of PRP in Avoiding Surgery

Delaying or Avoiding Orthopaedic Surgery with PRP

For many patients, PRP represents an attractive alternative to surgery, especially in cases of mild to moderate knee osteoarthritis or chronic knee injuries. Surgery, while often effective, carries risks such as infection, blood clots, and lengthy recovery periods. PRP, on the other hand, offers a minimally invasive solution that can significantly reduce pain and improve joint function without the associated risks of surgery. In patients with early-stage knee osteoarthritis, PRP has been shown to delay the progression of the disease and, in some cases, avoid the need for joint replacement surgery.

PRP as a Bridge to Surgery for Advanced Knee Conditions

In cases of advanced knee osteoarthritis, where joint replacement surgery may eventually be necessary, PRP can still play a valuable role as a bridge to surgery, providing symptomatic relief in the interim while patients prepare for more definitive interventions. By reducing inflammation and promoting tissue repair, PRP can improve the overall condition of the knee, potentially leading to better surgical outcomes when the time comes for joint replacement or other orthopedic procedures.

Future of PRP Therapy for Knee Pain and Injury Recovery

Ongoing Research and Advancements

Research into the use of PRP for knee pain and injury recovery is ongoing, with studies focusing on its efficacy, optimal treatment protocols, and potential combinations with other therapies. One area of interest is the combination of PRP with stem cells or other biologic therapies, such as hyaluronic acid. Some studies suggest that combining these treatments may result in synergistic effects, leading to better outcomes than using PRP alone.[17]

Other advancements include the development of more refined PRP preparation techniques, such as the use of leukocyte-rich PRP (LR-PRP) versus leukocyte-poor PRP (LP-PRP). While leukocyte-rich PRP contains higher concentrations of white blood cells, which may enhance inflammation and healing, leukocyte-poor PRP may be more appropriate for treating conditions where inflammation needs to be minimized, such as osteoarthritis.[18]

As research progresses, it is likely that PRP will become an even more integral part of musculoskeletal medicine, offering patients a safe, effective, and minimally invasive solution for managing knee pain and injury recovery.

Conclusion

PRP injections for knees represent a breakthrough in the treatment of knee pain and injury recovery. By utilizing the body’s natural healing processes, PRP offers a non-surgical option for patients with conditions such as osteoarthritis, chronic tendon injuries, and sports-related knee injuries.

For healthcare providers, PRP therapy presents a valuable tool for managing knee pain, improving function, and potentially delaying or avoiding the need for surgical intervention. With the development of systems like SELPHYL®, PRP preparation has become more reliable and accessible, further enhancing its role in clinical practice. As research into PRP therapy continues, healthcare practitioners can confidently consider this approach as part of a comprehensive treatment strategy for knee pain and injury recovery.

About the author: Dr. Ali is a medical journalist and copywriter.