Effect of Nonsteroidal Anti-Inflammatory Drug Restriction on the Efficacy of Platelet-Rich Plasma in Knee Osteoarthritis

Platelet-rich plasma (PRP) has shown promising results for reducing pain and improving function in people with knee osteoarthritis. However, it is unclear whether the use of nonsteroidal anti-inflammatory drugs after PRP may affect the clinical response. This study will compare ibuprofen, a nonsteroidal anti-inflammatory drug, with acetaminophen, which has no clinically relevant anti-inflammatory effect at the study dose. This is a randomized, controlled, parallel-group, double-blind clinical trial. Ninety adults with knee osteoarthritis will be randomly assigned in a 1:1 ratio to one of two groups. All participants will receive a single ultrasound-guided intra-articular injection of leukocyte-rich PRP. After the injection, participants will receive either ibuprofen 400 mg every eight hours or acetaminophen 500 mg every eight hours for five consecutive days. The medications will be provided in visually identical capsules. Participants and the physician performing the injection will remain unaware of the assigned medication. The primary outcome will be the change in knee pain measured using a visual analog scale six weeks after the injection. Secondary assessments will include knee function measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the use of additional pain medication during follow-up. Adverse events will be monitored through digital questionnaires at 24 hours, 48 hours, and seven days after the intervention, as well as during scheduled follow-up visits. Adverse events will be classified according to the Common Terminology Criteria for Adverse Events, version 5.0.