PRP for knee osteoarthritis may help some people with knee pain and function, but results vary and it does not rebuild worn knee cartilage. It uses a concentrated portion of your own blood, injected into the knee. If you are weighing a PRP shot, the useful questions are what your knee problem is, what the study results mean for you, what the clinic’s plan costs, and what happens if it does not help.
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What is knee arthritis, and why does it hurt?
Knee osteoarthritis is a joint condition in which tissues in the joint break down over time. The National Institute of Arthritis and Musculoskeletal and Skin Diseases explains that osteoarthritis can affect cartilage, bone, the joint lining, ligaments, tendons, and the meniscus in the knee.
You may notice pain with use, short-lived stiffness after sitting or resting, swelling after activity, less knee movement, or a grinding feeling. “Bone-on-bone” is a phrase people use when joint space has narrowed greatly. It describes the joint changes; it does not tell you by itself which option fits your knee.
What is a PRP injection in the knee?
Platelet-rich plasma, or PRP, starts with a blood draw. A clinician spins the sample in a centrifuge to concentrate platelets in plasma, then injects that preparation into the treatment area. Platelets are blood cells involved in clotting and contain proteins called growth factors.
WashU Medicine Orthopedics describes PRP as an outpatient procedure that generally takes less than an hour. It says the clinician may use ultrasound guidance for the injection. The exact preparation can differ between clinics, so ask what kind of PRP they use and how they prepare it.
Does PRP work for knee osteoarthritis?
PRP has shown improved pain, stiffness, and function in some studies, but the strength of the answer is limited by different PRP preparations, injection schedules, and study designs. A randomized controlled trial is a study that assigns people to different treatment groups so researchers can compare outcomes more fairly.
The 2013 Raeissadat trial enrolled 65 people with knee osteoarthritis; 60 completed the analysis. Participants received two leukocyte-rich PRP injections four weeks apart. At six months, the study measured pain, stiffness, physical function, and quality of life with the WOMAC and SF-36 questionnaires. Scores improved after treatment. The study also reported temporary local pain and swelling, and it did not include a comparison group. You can read the full Raeissadat PRP trial.
That is why a clinic should explain which result it expects to measure for you: pain during activity, stiffness, walking, daily tasks, or something else. For help separating a promising result from a result that answers your own question, see How to Read a Study.
Can PRP regrow knee cartilage?
PRP is being studied because platelets contain growth factors involved in tissue repair. The available knee studies often measure symptoms such as pain and function. They do not give you a clear basis to expect regrowth of established knee cartilage. Ask the clinician whether their goal is symptom improvement, function, or a change they can measure on imaging.
Why can my knee hurt more after a PRP shot?
Increased soreness for the first few days can happen after a PRP injection. WashU Medicine Orthopedics calls this an inflammatory phase and says it may take six to eight weeks to assess the response. The Raeissadat trial likewise reported injection-site pain, temporary stiffness, swelling, and dull pain in some participants.
An injection also places a needle into a sensitive joint. Your own knee inflammation and how much you load the knee afterward can affect how it feels. Contact the treating clinic promptly if your pain is getting worse rather than settling, or if you have symptoms that concern you. Your post-injection plan should come from the clinician who knows your knee and the technique used.
What are the possible PRP knee side effects?
| Possible issue | What the source reports |
|---|---|
| Short-term pain or soreness | WashU says many people have increased soreness and temporary pain afterward; the 2013 trial reported local pain. |
| Stiffness or swelling | The 2013 trial reported temporary knee stiffness and a feeling of swelling in some participants. |
| Bleeding, infection, nerve injury, or tissue damage | WashU lists these as less common risks of an injection procedure. |
| Allergic reaction | WashU lists allergic reaction as a less common risk. Ask what products besides your blood may be used during the procedure. |
This page is about PRP injected into the knee. PRP used on skin is a different procedure and has its own technique and aftercare questions.
What should you ask about activity, a brace, and medicines afterward?
Do not use a generic online timeline as your personal plan. WashU’s instructions say its patients are given individualized guidance; its general page advises limiting strenuous activity at the injection site for two weeks and notes that a joint may be immobilized with a sling or walking boot in some cases. A knee brace is therefore a question for the treating clinician, not an automatic part of every PRP knee injection.
Ask which activities are okay, when to return to exercise or physical therapy, whether a brace has a purpose in your case, and which pain medicines fit your plan. WashU says its patients are told not to use anti-inflammatory medicines for two weeks after the procedure and are given personalized instructions.
Is PRP worth it if you are 50, older, or have bone-on-bone arthritis?
Age alone does not answer that question. In the Raeissadat trial, participants averaged about 57 years old, and the study included people with radiographic osteoarthritis from grade 1 through grade 4. The researchers found a relationship between age and the amount of pain improvement, but the trial was small and was not designed to set an age cutoff.
Your diagnosis, arthritis severity, overall health, and treatment goal matter. WashU says PRP may be considered for an ongoing muscle, tendon, or joint condition that has not improved with activity changes, physical therapy, or medication, and that suitability depends on diagnosis, overall health, and the area treated. If you have advanced joint changes, ask the clinician to explain why PRP is or is not a sensible option for your particular knee.
PRP vs. hyaluronic acid and other ways to manage knee pain
Hyaluronic acid is another injection option discussed in knee osteoarthritis studies. The 2013 Raeissadat paper notes that trials have compared PRP with hyaluronic acid, but it also says there was no consensus on the best PRP concentration, number of injections, spacing, or long-term effect. A head-to-head comparison should include the exact injection plan, expected outcome, cost, and follow-up.
There is no single “new alternative” that is better for every knee. The National Center for Complementary and Integrative Health reports that tai chi improved pain, stiffness, balance, and physical function in osteoarthritis studies, and notes that its guideline source strongly recommends tai chi for knee or hip osteoarthritis. It also says acupuncture may help knee pain associated with osteoarthritis, although the evidence is controversial. A clinician may also discuss physical therapy, activity changes, medicines, braces, injections, or surgery based on the source of your pain and the condition of the joint.
How many PRP injections do you need, and do you need them forever?
There is no one standard schedule. The Raeissadat trial used two injections four weeks apart. WashU says some people need one injection while others may benefit from additional treatment, based on the condition and response to the first injection. A clinic should give you its planned number of injections, the reason for that plan, and the point at which it will reassess.
PRP is not a commitment to repeat injections forever. Ask what result would count as a meaningful response, how long the clinic will wait before judging that response, and what the next step would be if you do not get the result you hoped for.
What does PRP for the knee cost?
PRP is commonly an out-of-pocket procedure. WashU says Medicare currently covers PRP for chronic wound treatment and that most insurance plans do not cover PRP costs for the musculoskeletal uses discussed on its page. The price depends on the clinic, the preparation, imaging guidance, the number of injections, and follow-up. Ask for the full self-pay price before scheduling, including the consultation, blood processing, injection, imaging guidance, and follow-up visit.
Before your PRP appointment, ask these questions
- What is causing my knee pain, and what finding supports that diagnosis?
- What PRP preparation and injection schedule do you recommend for me?
- What outcome are we trying to improve, and when will we measure it?
- What side effects should prompt me to call the clinic?
- What is my activity, brace, physical therapy, and pain-medicine plan after the injection?
- What is the complete cost, and what follow-up is included?
- If PRP is not a match for my knee, what other options should we compare?
Bring these questions to your visit, along with your medication list and prior knee imaging if the clinic requests it. Procedure conversation questions can help you organize the discussion. If you believe you have had a serious problem after a regenerative-medicine procedure, the site’s side-effect reporting guide explains where to start.
By Regenerative Evidence Guide Editorial Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.
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