PRP before knee replacement is often promoted as a regenerative treatment for osteoarthritis. Platelet-rich plasma injections use a concentrated portion of your own blood and may reduce pain or improve function for some people.
PRP is not one standardized treatment, and it has not been shown to rebuild an arthritic joint. Understanding how it is prepared, what research has found, and what you are actually purchasing can help you evaluate the claims surrounding it.
What is platelet-rich plasma?
Platelets are small components of your blood that participate in clotting and carry proteins and signaling molecules involved in tissue responses. Plasma is the liquid portion of your blood.
To prepare PRP, a clinician draws a sample of your blood and places it into a centrifuge. The centrifuge separates components of the blood based on their density. A portion containing a higher concentration of platelets is then collected and injected into your knee joint.
Because the material comes from your own blood, PRP is described as an autologous product. That does not mean every PRP injection has the same composition. Preparation systems produce different platelet concentrations and may retain or remove varying amounts of white blood cells and other blood components.
Why PRP products are not all the same
Clinics may use different centrifuges, processing methods, injection schedules, and definitions of platelet-rich plasma. Some treatments use one injection, while others use a series. Some products are leukocyte-rich, meaning they contain more white blood cells. Others are leukocyte-poor.
These variations make PRP research harder to interpret. Two studies may both evaluate “PRP” while using biologically different preparations. The people enrolled, severity of osteoarthritis, comparison treatment, number of injections, and follow-up period can also differ.
If you are considering PRP, ask the clinician what preparation is being used, how many injections are proposed, and what evidence supports that particular approach. A general statement that “PRP works” does not provide enough information about the treatment being offered.
What PRP before knee replacement may change
The American Academy of Orthopaedic Surgeons states that PRP may reduce pain and improve function in people with symptomatic knee osteoarthritis. However, the recommendation is classified as limited because of concerns about the quality and consistency of the available evidence.
Several systematic reviews have reported better average pain or function outcomes with PRP than with hyaluronic acid injections. Some findings suggest that differences may become more noticeable several months after treatment rather than immediately.
PRP may improve symptoms for some people, but symptom improvement is not evidence that advanced arthritis has been reversed.
Not every high-quality trial has shown a benefit. In the RESTORE randomized clinical trial, three PRP injections were compared with saline injections in people with mild to moderate knee osteoarthritis. At 12 months, PRP did not produce a significant improvement in pain or medial tibial cartilage volume compared with placebo.
That trial does not settle every question about every PRP preparation. It does show why claims of predictable cartilage restoration or guaranteed pain relief go beyond the current evidence.
PRP does not regrow an arthritic joint
The word “regenerative” can easily be interpreted as meaning that PRP will regrow substantial amounts of cartilage or return an arthritic joint to its previous condition. Current clinical evidence does not support that promise.
PRP may influence inflammatory and biochemical activity inside your knee. It may reduce symptoms for a period of time. It has not been shown to correct a major deformity, reliably restore lost joint space, or eliminate the structural changes of advanced osteoarthritis.
This distinction is important when total knee replacement is already being discussed. If your symptoms improve, the treatment may still be useful. The value comes from what you can comfortably do, not from assuming that your joint structure has been restored.
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Who may be more likely to respond?
Research has not produced a reliable formula for predicting an individual response. Some studies suggest that people with mild to moderate osteoarthritis may be more likely to benefit than people with severe joint changes. Age, body composition, symptoms, activity level, and the PRP preparation may also influence the result.
A person with advanced osteoarthritis may still report symptom relief, but PRP is less likely to change a larger structural problem enough to eliminate the need for surgery.
If you proceed, identify a few functional markers before the injection. These might include walking tolerance, stair use, sleep interruption, standing tolerance, or participation in strengthening. Reassessing the same activities later provides more useful information than relying on a general memory of pain.
What to expect around the procedure
The appointment usually includes a blood draw, preparation of the PRP, and an injection into your knee joint. Ultrasound may be used to guide placement. Temporary soreness or swelling can occur afterward, and improvement is not usually immediate.
Clinicians use different instructions about activity and medications before and after PRP. Some ask patients to avoid certain anti-inflammatory medications for a period of time, but medication changes should come directly from the clinician managing the procedure and the professional who prescribed the medication.
Possible complications include pain, bleeding, infection, and injury related to the injection. Using your own blood reduces concern about an allergic reaction to the injected material, but it does not make the procedure risk-free.
Cost and surgical timing
PRP for knee osteoarthritis is frequently not covered by insurance. The price may include one injection or a proposed series, so ask for the total expected cost before agreeing to treatment.
Also ask how long the clinician expects a fair trial to take and what happens if the first injection does not help. Paying for additional injections without a clear method for evaluating the first treatment can turn an uncertain option into a costly sequence.
If total knee replacement may occur within the next several months, discuss the proposed injection with your surgeon before scheduling it. Evidence about PRP timing and infection risk before joint replacement is less established than the evidence concerning corticosteroid injections. Your surgeon or hospital may still require a specific interval between any joint injection and surgery.
How PRP fits into the larger plan
PRP is one possible symptom-management tool. It does not replace strengthening, physical activity, weight management when applicable, medication review, or preparation for surgery.
If an injection improves your comfort, that period may provide an opportunity to build strength, improve stamina, and participate more fully in prehabilitation. If it does not help, that result may clarify the next conversation with your orthopedic surgeon.
If surgery is becoming more likely, download the free 2-Week Knee Replacement Launch Plan. You can also explore The Knee Replacement Game Plan™ for a more complete approach to preparing before surgery.
The next episode concludes this injection series by comparing cortisone, gel injections, and PRP so you can see how their purposes, evidence, cost, and limitations differ.
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References
- American Academy of Orthopaedic Surgeons. Management of Osteoarthritis of the Knee (Non-Arthroplasty): Evidence-Based Clinical Practice Guideline. 3rd ed. Published August 31, 2021.
- Bennell KL, Paterson KL, Metcalf BR, et al. Effect of intra-articular platelet-rich plasma vs placebo injection on pain and medial tibial cartilage volume in patients with knee osteoarthritis: the RESTORE randomized clinical trial. JAMA. 2021;326(20):2021-2030. doi:10.1001/jama.2021.19415
- Belk JW, Kraeutler MJ, Houck DA, Goodrich JA, Dragoo JL, McCarty EC. Platelet-rich plasma versus hyaluronic acid for knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Am J Sports Med. 2021;49(1):249-260. doi:10.1177/0363546520909397
- Li S, Yang G, Zhang H, et al. Multiple injections of platelet-rich plasma versus hyaluronic acid for knee osteoarthritis: a systematic review and meta-analysis of current evidence in randomized controlled trials. J Orthop Surg Res. 2023;18(1):234. doi:10.1186/s13018-023-03784-4
- Kim JH, Park YB, Ha CW, et al. Are leukocyte-poor or multiple injections of platelet-rich plasma more effective than hyaluronic acid for knee osteoarthritis? A systematic review and meta-analysis of randomized controlled trials. Arch Orthop Trauma Surg. 2023;143(7):3879-3897. doi:10.1007/s00402-022-04690-5
Educational Disclaimer: This article provides general educational information and is not medical advice. It does not determine whether PRP is appropriate for a specific person, diagnose the source of symptoms, or replace guidance from a surgeon, physician, physical therapist, or other licensed healthcare professional. Injection decisions, medication changes, and timing before surgery must be individualized.