PRP therapy for the knee is a treatment where a concentrated solution of your own platelets is injected into the knee joint to reduce pain and inflammation. It’s most commonly used for knee osteoarthritis, though it’s also applied to tendon injuries, meniscal tears, and as a supplement to ligament reconstruction surgery. Most patients report 6 to 12 months of pain relief after treatment, according to clinicians at Mayo Clinic.
How PRP Works Inside the Joint
Platelets are blood cells best known for clotting, but they also carry a dense payload of proteins that regulate healing. When injected into a knee joint, they release growth factors that stimulate tissue repair and the formation of new blood vessels, along with proteins that help build the structural matrix of cartilage and other connective tissue.
The other major effect is on inflammation. PRP dials down the inflammatory signals that drive osteoarthritis pain, particularly the molecules responsible for cartilage breakdown and joint swelling. At the same time, it boosts anti-inflammatory signals and shifts the immune cells in the joint toward a repair-oriented state rather than a destructive one. This combination of dampening inflammation and promoting tissue maintenance is what distinguishes PRP from treatments that only mask symptoms.
Knee Conditions Treated With PRP
Osteoarthritis is the most studied and most common reason people get PRP injections in the knee. The treatment has been used across a range of severity, from mild cartilage wear to more advanced joint degeneration. That said, results tend to be strongest in mild to moderate osteoarthritis, where there’s still cartilage left to preserve.
Beyond osteoarthritis, PRP has been used for:
- Patellar tendinopathy (jumper’s knee), where PRP injections combined with physical therapy have shown benefits over physical therapy alone in chronic cases
- Meniscal repair, where PRP added during surgery has shown modest improvements in outcomes, particularly for tears that extend into areas with poor blood supply
- ACL reconstruction recovery, where PRP applied to the graft and harvest sites has been associated with better knee function at one year
How PRP Compares to Other Injections
A meta-analysis of 20 randomized controlled trials found that PRP reduced pain more effectively than hyaluronic acid (a lubricating gel injection) at both 6 and 12 months. PRP also produced better functional recovery in the short term and better long-term pain relief. Importantly, PRP did not carry a higher risk of side effects compared to hyaluronic acid.
Multiple studies have also compared PRP to steroid injections for knee osteoarthritis. Steroids typically provide faster initial relief but wear off within weeks to a few months. PRP takes longer to kick in but generally lasts longer. For people seeking sustained improvement rather than a quick fix, PRP tends to come out ahead in the research, though steroids remain useful for acute flare-ups.
What Happens During the Procedure
The entire process typically takes under an hour. A clinician draws a blood sample from your arm, then places it in a centrifuge, a machine that spins rapidly to separate blood components. This concentrates the platelets into a small volume of plasma, typically at several times the concentration found in normal blood.
That concentrated solution is then injected directly into the knee joint. Some clinicians use ultrasound imaging to guide the needle into the precise location. The injection itself feels similar to any other joint injection: brief pressure and a sting that fades quickly.
Recovery and Activity Restrictions
The first few days after a PRP injection often involve some increased soreness and swelling in the knee. Ice the area for 15 to 20 minutes every few hours during this period. One critical rule: avoid anti-inflammatory medications like ibuprofen or naproxen for two weeks after the procedure. These drugs interfere with the inflammatory cascade that PRP is designed to harness. Use acetaminophen (Tylenol) for pain instead.
For the first two weeks, avoid strenuous activity and exercise involving the knee. Your doctor may have you use a walking boot or brace during this window. Physical therapy typically starts at the two-week mark, and most people return to normal activity around six weeks after the injection.
Types of PRP Formulations
Not all PRP is the same. The two main formulations differ in whether they include white blood cells (leukocytes). Leukocyte-rich PRP contains a higher concentration of these immune cells, while leukocyte-poor PRP filters most of them out. Some researchers have recommended leukocyte-poor PRP for osteoarthritis, based on the concern that white blood cells could increase inflammation inside the joint. However, clinical trials comparing the two have found similar improvements at 12 months for knee osteoarthritis patients. The question of which formulation is truly better remains unresolved.
Side Effects and Safety
Because PRP is made from your own blood, the risk of allergic reaction or disease transmission is essentially zero. The most common side effect is a temporary flare of pain and swelling at the injection site, which typically resolves within a few days. A literature review identified infection as the most commonly reported serious adverse event associated with PRP therapy, though this remains rare with proper sterile technique. Other uncommon complications include localized inflammation and nodule development at the injection site.
Cost and Insurance Coverage
PRP injections are rarely covered by health insurance. Because patients pay out of pocket, pricing varies widely with no real standardization. A single injection typically costs between $500 and $1,500, with the average falling around $1,000 to $1,200. Since many treatment protocols call for multiple injections (often a series of three), the total cost per patient averages closer to $3,000. Prices vary significantly by region and clinic.
What Professional Guidelines Say
The American Academy of Orthopaedic Surgeons (AAOS) has reviewed the evidence on PRP for knee osteoarthritis but stops short of a strong endorsement. Their 2021 guidelines on nonoperative management of knee arthritis rated PRP with a low strength of evidence and a low grade of recommendation. This doesn’t mean PRP doesn’t work; it reflects the fact that study designs, PRP formulations, and treatment protocols vary so much across trials that it’s difficult to issue a blanket recommendation. Many orthopedic specialists still offer PRP as a reasonable option for patients with mild to moderate osteoarthritis who haven’t responded well to other conservative treatments.