Want Dr. Calendine’s articles to stand out in your Google and AI search results? Add him as a preferred source (one tap).
PRP injections for knee arthritis come up in my Franklin clinic almost every week. Patients ask me if a shot made from their own blood can really quiet an aching knee, and whether it can keep them out of the operating room. The honest answer is: sometimes, for the right knee, for a limited stretch of time.
After more than twenty years focused on hip and knee care, and more than 700 joint replacements a year, I spend a lot of my day telling patients they do not need surgery yet. PRP is one of the tools I discuss in that conversation. Here is how I explain it across the desk.
What Are PRP Injections and How Do They Work?
PRP stands for platelet-rich plasma: your own blood, spun in a centrifuge so the platelets are concentrated, then injected into the knee joint. Platelets are the blood cells best known for clotting, but they also carry growth factors, which are proteins that signal tissue to heal and inflammation to settle down.
The visit itself is simple. We draw a small tube of blood from your arm, spin it for a few minutes, and inject the platelet-rich layer into the knee, often with ultrasound guidance so the needle lands exactly where it should.
The whole process takes well under an hour. Most people are back to normal daily activity within a day or two.
What PRP injections are supposed to do in an arthritic knee
Osteoarthritis is a wearing down of the smooth cartilage that caps the ends of your bones. The goal of PRP is not to grow that cartilage back. The goal is to change the chemistry inside the joint: less inflammation, less pain signaling, and a calmer environment for the cartilage you still have.
That distinction matters. Some clinics market PRP as a regenerative cure. I tell my patients to think of it as a symptom treatment with a longer runway than cortisone, not a repair job.
Can PRP Injections Help Knee Arthritis?
Yes, PRP injections can help many people with mild to moderate knee arthritis, and the relief often lasts 6 to 12 months in patients who respond. Large academic centers report that roughly 60 to 70 percent of carefully chosen patients get at least a 50 percent improvement in pain and function over that window.
Notice the qualifiers: mild to moderate arthritis, carefully chosen patients. That is where honest medicine lives.
In my practice, the patients who do best with nonsurgical care share a pattern. They have arthritis on X-ray but still have joint space left. They are active, motivated, and working on strength and weight alongside any injection. PRP can buy that patient real time.
The patient with a bone-on-bone knee is a different story. Once the cartilage is gone, no injection restores it, and the research on PRP in severe arthritis is much weaker. I would rather tell you that plainly than sell you a series of expensive shots that disappoint you.
What Does the Research Say About PRP Injections?
The research on PRP injections is genuinely mixed, and any doctor who tells you otherwise is simplifying. Meta-analyses (studies that pool many trials together) found PRP eased pain and improved function better than hyaluronic acid gel shots and better than placebo saline. The edge was clearest past the three month mark.
Compared with cortisone, the pattern flips over time. Steroid shots often work faster in the first 4 to 6 weeks, while PRP tends to pull ahead at 3 to 6 months and can hold its benefit longer.
At the same time, smaller studies found little or no lasting benefit, with scores drifting back to baseline within weeks of the final shot. Study quality varies. PRP preparations differ from clinic to clinic, and there is still no standard recipe for how strong the platelet mix should be.
Why do PRP study results disagree so much?
PRP study results disagree mostly because PRP itself is not one product. Platelet concentration, white blood cell content, activation method, and injection schedules all vary between studies, so pooling them is messy.
Patient selection matters just as much. Trials heavy with severe, bone-on-bone arthritis show weaker results than trials of earlier disease. That mirrors exactly what I see in the clinic.
Who Is a Good Candidate for PRP Injections?
The best candidate for PRP injections has mild to moderate knee osteoarthritis, ongoing pain despite exercise and simple measures, and a wish to delay or avoid knee replacement. Younger, active patients who are not yet ready for surgery often fit this profile well.
Here is what I look at before recommending PRP or any knee injection:
- Your X-rays: how much joint space and alignment you still have
- What you have already tried: physical therapy, activity changes, weight management, anti-inflammatory medication
- Your goals: golfing again, keeping up with grandkids, or simply sleeping without knee pain
- Your budget: insurance rarely covers PRP, so the cost is usually out of pocket
When PRP is not the right choice
PRP is not the right choice for severe, end-stage arthritis, active infection, certain blood disorders, or a knee that is badly deformed or unstable. It is also the wrong choice when it is used to put off a conversation the knee is already forcing.
If your knee wakes you at night, limits you to a block of walking, and shows bone touching bone on X-ray, another injection is usually a detour. That knee deserves a frank talk about knee replacement, including modern options like robotic-assisted surgery with the Mako® system that I use for precise implant placement.
What Are the Risks and Side Effects of PRP?
PRP is a low-risk procedure because it uses your own blood, so allergic reactions are very unlikely. The most common side effects are soreness, stiffness, and mild swelling at the injection site for a day or two.
Rare risks include infection, bleeding, and nerve irritation, the same short list that applies to any joint injection. One practical note: PRP is FDA-cleared to prepare but not FDA-approved as a treatment for arthritis, which is a big part of why most insurance plans do not pay for it.
Plan on pausing anti-inflammatory medicines like ibuprofen around the injection, since they can blunt platelet function and may reduce the benefit.
What Should You Do Next About Your Knee Arthritis?
Start with an accurate picture of your knee, not a product. A standing X-ray, a proper exam, and a talk about your goals will show us the right path. That might be PRP injections, other nonsurgical joint pain treatments, or a surgical discussion.
I see patients from Franklin, Nashville, Columbia, Spring Hill, and across Middle Tennessee at the Bone and Joint Institute of Tennessee, 3000 Edward Curd Lane, Franklin, TN 37067. You can call (615) 791-2630 or schedule an appointment online.
Whatever we decide together, the plan will be built on evidence and on your goals, not on the newest thing being advertised. That is the standard your knee deserves.
Medical disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk with a qualified orthopaedic provider about your specific condition before making treatment decisions. Individual results vary. Dr. Calendine serves as a consultant to Stryker, the manufacturer of the Mako robotic platform.
Watch: Can PRP Injections Heal Your Knee?
Dr. Calendine gives the 38 second answer on whether PRP injections can heal an arthritic knee, and what they realistically do instead.
