Should You Continue Aspirin Before PRP Injection for Your Right Knee?
You should stop aspirin 3–5 days before your platelet-rich plasma (PRP) injection to maximize the effectiveness of the treatment, unless you have a coronary stent or recent cardiovascular event requiring aspirin for secondary prevention—in which case you must consult your cardiologist before stopping. 1, 2
Why Aspirin Interferes with PRP Efficacy
- Aspirin irreversibly inhibits platelet cyclooxygenase-1 (COX-1), blocking the degranulation process that releases growth factors and cytokines essential for PRP's therapeutic effect. 1, 2
- Studies demonstrate that aspirin significantly decreases platelet aggregation in 268 patients, which directly undermines the mechanism by which PRP promotes tissue healing and regeneration. 1
- The inhibitory effect persists for 7–10 days (the lifespan of platelets), but functional recovery sufficient for PRP efficacy occurs within 3–5 days as new platelets enter circulation. 3, 2
Recommended Aspirin Discontinuation Timeline for PRP
- Stop aspirin 3 days before your PRP injection if you are taking it for primary prevention (no history of heart attack, stroke, or stent). 3, 4, 1
- Stop aspirin 5 days before the procedure if you want to ensure maximal platelet function recovery, particularly for higher-dose aspirin regimens. 3, 4, 2
- Naproxen requires 24–48 hours of discontinuation, ibuprofen 6–12 hours, but aspirin's irreversible mechanism necessitates the longer 3–5 day window. 2
Critical Exception: Cardiovascular Disease Patients
If you are taking aspirin for secondary cardiovascular prevention (history of myocardial infarction, stroke, peripheral arterial disease, or coronary stent), DO NOT stop aspirin without explicit cardiologist approval. 5, 6
- Discontinuing antiplatelet therapy increases your absolute risk of stroke recurrence or major cardiovascular events by approximately 2% within 30 days. 5, 4
- Patients with coronary stents must continue aspirin regardless of stent type or timing, as premature discontinuation markedly increases risk of catastrophic stent thrombosis, death, and myocardial infarction. 5
- For these high-risk patients, the cardiovascular protection outweighs the potential reduction in PRP efficacy—proceed with the injection while continuing aspirin. 5, 6
Practical Decision Algorithm
| Your Aspirin Indication | Action Before PRP | Rationale | Citation |
|---|---|---|---|
| Primary prevention only (no cardiovascular disease) | Stop 3–5 days before | Maximize PRP platelet function without cardiovascular risk | [1,2] |
| Secondary prevention (prior MI, stroke, PAD) | Consult cardiologist; likely continue | 2% absolute risk increase in cardiovascular events if stopped | [5,4] |
| Coronary stent (any type, any timing) | Continue aspirin | Catastrophic stent thrombosis risk outweighs PRP optimization | [5] |
| Over-the-counter use for minor aches | Stop 3–5 days before | No cardiovascular indication to continue | [1,2] |
When to Resume Aspirin After PRP
- Restart aspirin 12–24 hours after your PRP injection once any injection-site bleeding has stopped. 5, 4
- For patients who continued aspirin due to cardiovascular indications, no interruption is needed—simply proceed with the injection. 5, 6
Common Pitfalls to Avoid
- Do not assume all NSAIDs behave like aspirin. COX-2-selective NSAIDs (celecoxib) do not significantly inhibit platelet function and do not need to be stopped before PRP. 1
- Do not stop aspirin for 7–10 days as traditionally recommended for surgery. PRP is a minimally invasive injection with negligible bleeding risk, and 3–5 days is sufficient for platelet recovery. 3, 4, 2
- Do not forget to disclose over-the-counter aspirin or combination products (e.g., Excedrin, Alka-Seltzer) during your pre-procedure medication reconciliation. 3
- Acetaminophen (Tylenol) is a mild COX-1 inhibitor but does not require discontinuation before PRP. 1, 2
Evidence Quality and Nuances
- The 2022 systematic review in Orthopaedic Journal of Sports Medicine provides Level 2 evidence that aspirin significantly decreases platelet aggregation without affecting platelet count, supporting discontinuation before PRP. 1
- The 2024 Cureus review reinforces that aspirin's irreversible COX-1 inhibition requires a time-dose relationship for deferral, with 3–5 days being the evidence-based window. 2
- Perioperative aspirin guidelines (designed for surgical bleeding risk) are not directly applicable to PRP injections, which prioritize platelet function over bleeding risk. 3, 5
- A 2024 study in American Journal of Sports Medicine demonstrated that higher platelet concentration in PRP correlates with better clinical outcomes in knee osteoarthritis, underscoring the importance of optimizing platelet function by stopping aspirin. 7