by Dr. Walter I. Sussman

Platelet-rich plasma (PRP) injections are increasingly used to treat knee osteoarthritis. Because PRP is produced from a patient’s own blood, it is sometimes assumed to have few or no side effects. Like any injection, however, PRP can cause temporary pain, swelling, or other reactions.

A 2025 meta-analysis published in Arthroscopy specifically examined complications following PRP injections for knee osteoarthritis (Fucaloro et al, 2025). The authors analyzed 24 randomized controlled trials involving 2,751 patients, including 1,318 patients who received PRP. Comparators included hyaluronic acid (HA), corticosteroid injections, and placebo injections.

PRP Has a Similar Safety Profile to Other Active Injections

Perhaps the most important finding is that PRP did not have a significantly higher risk of complications than either hyaluronic acid or corticosteroid injections.

When PRP was compared specifically with HA, there was no significant difference in complications (OR 1.33, P=.22). This remained true when the researchers examined leukocyte-rich versus leukocyte-poor PRP, single versus multiple injections, and whether the PRP was activated before injection.

Similarly, PRP did not have significantly greater odds of complications than corticosteroid injections (OR 3.07, P=.35), although fewer studies were available and there was greater variability among these trials.

These comparisons are particularly relevant because HA and corticosteroids represent active treatments that are commonly considered alongside PRP for knee osteoarthritis.

How Common Is Pain After a PRP Injection?

The most common complication following PRP was temporary pain after the injection. Post-injection pain occurred in 7.2% of patients receiving PRP. Joint swelling or effusion occurred in approximately 4.8% of PRP patients.

This is important when counseling patients. Some soreness or an inflammatory response after PRP is not unusual and does not necessarily indicate that something has gone wrong.

Most reported reactions occurred within the first 24 hours to one week following treatment. Only one severe pain reaction was reported and resolved within one week.

Why Were More Side Effects Reported With PRP Overall?

In this paper, PRP did have more reported adverse events when compared with saline placebo injections. This helps explain why the overall complication rate in the Fucaloro er al. paper appeared higher when PRP was compared with all other injections combined.

The difference should also be interpreted in the context of what was considered a complication. Most adverse events were temporary post-injection reactions, particularly pain and swelling. Post injection pain occurred in 7.2% of PRP patients, while joint effusion occurred in 4.8%.

Most reported reactions occurred within the first day to week following injection. Only one severe pain reaction was reported, and it resolved within one week.

Are Serious Complications Possible?

Serious complications appeared to be uncommon. No infections were reported among the 2,751 patients included in these randomized trials, and the review found no serious events such as allergic reaction, thrombosis, or hematoma attributed to PRP.

However, this does not mean that serious complications are impossible.

What Should Patients Take Away?

PRP injections for knee osteoarthritis are not risk-free. Temporary soreness, swelling, or an inflammatory reaction can occur after treatment and should be discussed before the procedure.

However, the more clinically meaningful finding is that PRP had a complication profile similar to hyaluronic acid and corticosteroid injections.

PRP produced more reactions than an inert saline injection, but these were overwhelmingly mild to moderate and short-lived. The randomized trials included in the analysis reported no infections.

For patients considering PRP for knee osteoarthritis, these findings provide useful context: PRP may cause temporary post-injection symptoms, but its overall safety appears comparable to other commonly used active knee injections.

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References

Fucaloro SP, Bragg J, Berhane M, Mulvey M, Krivicich L, Zink T, Salzler M. Complications of Platelet-Rich Plasma Injection for Knee Osteoarthritis Are Similar to Those of Corticosteroids and Hyaluronic Acid but Are Significantly Greater Than Those of Placebo Injections: A Meta-analysis of Randomized Controlled Trials. Arthroscopy. 2025 Nov;41(11):4789-4803. doi: 10.1016/j.arthro.2025.05.018. Epub 2025 May 21. PMID: 40409439.