PRP Knee Injection Reviews: Benefits & Side Effects

I regularly discuss knee osteoarthritis treatments here since many of my patients inquire about it.

In recent years, some people have been asking for my physical therapist’s opinion on platelet-rich plasma (PRP) for knee osteoarthritis or cartilage issues.

As usual, I’ve delved deep into the subject by reading scientific publications on this therapy. My aim is to assist you in gaining a clearer understanding of the potential benefits and risks of this therapy in your specific case, considering your expectations and personal criteria.

Happy reading! If you have any comments, additional information, questions, or corrections, feel free to leave them in the comments section 🙂.

What exactly is platelet-rich plasma (PRP)?

Platelet-rich plasma (PRP) is one of the many therapies proposed primarily to:

1. Alleviate pain associated with knee osteoarthritis (gonarthrosis).
2. Delay or prevent knee cartilage wear and tear.

The fact that this technique is offered doesn’t necessarily mean there is a wealth of evidence and experience regarding its effectiveness and potential side effects. That’s why I’ve decided to write this article!

What does PRP therapy involve?

When undergoing this therapy, three main steps are followed:

1. Your blood is drawn.
2. Various treatments are applied to your drawn blood to increase the concentration of platelets beyond its normal levels, hence the term “platelet-rich.”
3. The transformed product is then injected into a specific area of the body.

How can we explain the potential benefits of PRP injections for osteoarthritis?

Platelets are blood cells rich in growth factors and proteins, playing a crucial role in tissue repair and regeneration. This is why it is believed that by injecting blood with a higher platelet count than usual, something positive will occur.

Particularly, when it happens at the site of one of your joints that’s starting to deteriorate. It is assumed that the surplus of platelets will release growth factors that will:

1. Reduce inflammation.
2. Promote the formation of new cartilaginous tissues.

This is the theory, which is quite logical. Ideally, it needs to be tested on individuals to see if:

1. The effect is genuinely significant.
2. How long it lasts.
3. The quantity of the product or the number of sessions required.
4. If there are any side effects.

This is why I delve deeper into the effectiveness of PRP therapy, evaluated through clinical studies on real people, particularly those with knee osteoarthritis.

How does PRP therapy for knee osteoarthritis work?

PRP therapy for knee osteoarthritis generally involves the following steps:

1. You consult a doctor who performs this type of therapy, often a rheumatologist, orthopedic surgeon, or sports medicine physician. After an evaluation, you determine with the doctor if this therapy is potentially relevant for you.
2. If you decide to undergo PRP therapy, a blood sample is taken, similar to a traditional blood draw.
3. The collected blood is then placed in a special centrifuge, separating the different blood components and creating the PRP, which is platelet-rich plasma.
4. Once the platelets are concentrated, the PRP is prepared by mixing the PRP with an anticoagulant to obtain a solution rich in platelets.
5. Finally, your doctor injects the PRP directly into your knee, typically using an ultrasound simultaneously to ensure precise placement of the PRP.

Since when has this technique been used for knee osteoarthritis?

Platelet-rich plasma (PRP) has been utilized in various medical fields in chronological order:

1. In the 1970s, it was initially used in the field of hematology (blood disorders) to treat individuals with low platelet counts.
2. In the 1980s and 1990s, PRP began to be employed in surgical procedures such as maxillofacial surgery and plastic surgery (cosmetic surgery).
3. Subsequently, it has been used in rheumatology, sports medicine, orthopedics (for osteoarthritis), and other medical sectors.

Source: Gupta 2021

So, there are several decades of potential experience regarding both the positive and negative effects of PRP, including its application in knee osteoarthritis.

I will now detail what studies say about its effectiveness in people with gonarthrosis.

What are the benefits of PRP for knee arthritis?

Here are some thoughts and data to help you decide whether PRP injections may be beneficial for you.

How to find out about the technique’s effectiveness?

First, I will examine the various methods available to determine the effectiveness of platelet-rich plasma, as with any knee osteoarthritis treatment, even natural ones.

Testimonials

Testimonials are often the first thing people come across, whether through personal accounts from acquaintances or on the internet. However, there are several issues with testimonials.

It’s difficult to ascertain whether the person used other treatments alongside or before using PRP. Additionally, we don’t know if the people’s problems and expectations were similar to ours.

Osteoarthritis symptoms are not constant and can vary from day to day. Therefore, it’s challenging to determine based on a single testimonial whether the treatment was genuinely effective for a particular symptom, or if the pain or any other symptom simply fluctuated or naturally regressed.

Furthermore, there is a selection process in testimonials:

• Professionals who partly depend on PRP (even if well-intentioned and sincere) are more likely to highlight positive testimonials (the same goes for intermediaries who earn money by referring to these treatments).
• In contrast, highly satisfied or dissatisfied patients are more likely to provide testimonials than those who were indifferent to the technique.

To illustrate this, here are two different testimonials following platelet-rich plasma injections for knee osteoarthritis:

How to decide to give more weight to positive testimonials than negative ones?

For all these reasons, I personally try to assign limited importance to testimonials, whether for solutions against osteoarthritis or anything else.

The opinions of professionals and experts

Some individuals dedicate hours each week to assisting people suffering from osteoarthritis, including physiotherapists, doctors, surgeons, or other healthcare professionals.

Others work in research laboratories to study the physiology of osteoarthritis or the progression of symptoms in individuals with osteoarthritis.

These professionals have acquired a certain level of expertise in this field.

It is reasonable to assume that their opinions are probably more reliable than those of an average person who has less frequent contact with individuals affected by osteoarthritis.

However, it is important to ensure:

• They are indeed experts specifically in osteoarthritis.
• Their statements are not discredited by the majority of other experts in the field.

If one has limited confidence in a few testimonials or the words of a single expert, what can they turn to? Scientific publications are there to address this limitation.

Scientific studies on osteoarthritis and PRP injections

Fortunately, there is a vast amount of scientific publications on osteoarthritis. To date, over 150,000!

With more than 10,000 new studies published each year, and several hundred on PRP injections!

The publication system also has its limitations and flaws. However, with scientific publications, their authors are required to:

• Devote a significant amount of time to reflect on the subject.
• Formulate hypotheses.
• Evaluate whether they align with our knowledge in biology and other areas.
• Subject their ideas to scrutiny by other experts who can identify weaknesses.

Now, I will present the results of study syntheses published specifically on knee osteoarthritis and PRP injections.

I focus on syntheses rather than selecting 1 or 2 studies (as often seen in other articles on the subject).

What do the most recent studies say on PRP knee injections?

When there are many studies on a topic, research teams conduct what are known as “systematic reviews” or “meta-analyses.” They select the highest-quality studies and draw conclusions about treatments with the best benefit-risk ratio.

Between January 2020 and June 2023, more than 20 scientific publications sought to summarize and evaluate the quality of evidence on the effectiveness and side effects of PRP injections in knee osteoarthritis. For someone who spends a lot of time consulting these types of publications on various medical topics, I can tell you that’s a lot.

Here are the statements and findings from a Mexican research team 🇲🇽 (Simental 2023) that recently published a mega-synthesis of all these studies in July 2023, focusing on those that assess the effectiveness of PRP injections compared to other therapies or a placebo, rather than studies comparing one type or number of PRP injections to another.

Their initial assessment:

1. The use of platelet-rich plasma as a therapeutic intervention for knee osteoarthritis has generated significant interest since 2008.
2. There are many scientific publications, and most results reported in clinical trials and fundamental science studies show an effect within a year following the injection.
3. However, the use of platelet-rich plasma in clinical practice still presents controversial aspects. The primary recommendations for clinicians do not recommend its use.
4. Its effectiveness in slowing the progression of knee osteoarthritis has not been proven yet. Even when greater effectiveness than hyaluronic acid and a placebo was found, with a follow-up of at least one year, the studies conducted are highly diverse and not necessarily very rigorous. It is really uncertain whether the effect is significant for individuals.

Here are the conclusions of the authors, after reading and studying the results of all the syntheses:

Currently, the results of randomized clinical trials seem to favor the use of PRP over other osteoarthritis treatments, such as hyaluronic acid injections, for improving pain scales in the short and medium term (6 to 12 months).

However, the poor methodological quality of available trials and the variability of PRP preparations prevent a definitive demonstration of clinical effectiveness. (…) PRP is more effective in those with less cartilage degeneration or a lower grade of osteoarthritis. (…)

In conclusion, at present, the therapeutic potential of PRP products in osteoarthritis remains unexplored, and without further standardization, its clinical effectiveness will remain an open debate.

Simental et al. 2023

The research team says that we really need to change the way we evaluate the effectiveness of this technique if we hope to say something about it. Instead of repeatedly conducting studies that cannot provide us with more than what they currently do.

Another point to consider is adverse effects. What we know to date (Li 2023):

• Pain at the injection site is generally more significant than when receiving hyaluronic acid.
• There can also be knee swelling/edema (similar to hyaluronic acid injections).
• Potential long-term side effects are poorly evaluated.

Summary of the Advantages and Disadvantages of PRP in Knee Osteoarthritis

An Italian team 🇮🇹 has compiled a summary of the advantages and disadvantages of platelet-rich plasma injections in knee osteoarthritis (Szwedowski, 2021).

Advantages	Disadvantages
Simple and minimally invasive technique (no surgery, incisions, or scarring)	Small risk of pain or other complications at the injection site
Immediate preparation of PRP, no need for storage installations	Lack of standardized method for PRP preparation and administration
Safety of PRP preparations due to the use of unaltered, own cells	Formation of scar tissue and calcification at the injection site
PRP therapy can restore both structure and function; intra-articular PRP injections can simultaneously reduce synovial inflammation, protect cartilage, and alleviate pain	Optimal treatment time and platelet and leukocyte isolation methods, as well as the optimal concentration of these components for maximum beneficial effects, remain unknown
Minimization of blood-origin contaminants	Rare infections at the injury site and allergic reactions
Reduced recovery period associated with PRP	The optimal frequency and volume of PRP injections remain unknown
Biocompatibility and reduced risk of rejection or allergic reactions; preparations do not induce an immune response	Contraindications for administration in individuals with platelet dysfunction syndromes, thrombocytopenia, hyperfibrinogenemia, hemodynamic instability, sepsis, acute and chronic infections, chronic liver disease, and anticoagulant therapy

Why Do We Find Contradictory Information on the Benefits of PRP?

You’ve probably come across very different opinions from mine. Some people claim that PRP injections are effective, citing studies that have demonstrated their efficacy.

Here are the explanations I see for these differences in interpreting data from studies. I am, of course, referring only to those who rely on research results because that’s what I consider most trustworthy, even though it’s not perfect.

1. The search for sensationalism: The media often seeks sensational stories and emphasizes positive or spectacular results. This can lead to the selection of studies that show positive effects of PRP, while studies that do not show a significant effect are neglected or underrepresented. This is called cherry-picking, where one unconsciously selects things that align more with a particular narrative.
2. Lack of contextualization: Scientific study results can sometimes be presented in a simplistic or sensationalist way in the mainstream media without considering the nuances and limitations of the research. Specific study details, such as sample size, methodology, outcome measures, etc., can significantly impact the conclusions. Omitting this important information can contribute to confusion and misinterpretation of results.
3. Meeting patient expectations: Some individuals are willing to do anything to find a solution to their osteoarthritis problem. As healthcare professionals, it’s difficult to accept that there’s no miracle cure for osteoarthritis, and we have nothing groundbreaking to offer our patients. To meet the pressing demand, we sometimes propose things (which we might not offer to people who consult us differently).
4. Confusion between correlation and causation: Some professionals see people genuinely improving after PRP injections. Other uncontrolled factors (in real life and in studies) may explain the observed improvements.

For all these reasons, I will try to take a step back when confronted with any new article (whether in mainstream media or not) claiming that “the effectiveness of PRP injections for knee cartilage regeneration has been proven.”

What Are the Alternatives to Platelet-Rich Plasma for Knee Arthritis?

At this point, you might be wondering, “Okay, PRP injections may not be the best option for me. What should I do instead? What really works for knee osteoarthritis?”

For more information on these recommendations, you can refer to my article on the benefits of walking for knee osteoarthritis.