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.

Inclusion criteria

• Age between 18 and 80 years
• Knee pain for at least 3 months
• Radiographic evidence of knee osteoarthritis classified as Kellgren-Lawrence grade I, II, or III
• Ability and willingness to provide written informed consent

Exclusion criteria

• Body mass index of 35 kg/m2 or higher
• Pregnancy or breastfeeding
• Diabetes mellitus with glycated hemoglobin greater than 6.5%
• Hematologic disease, including anemia, coagulopathy, or thrombophilia
• Hemoglobin below 11 g/dL
• Hematocrit below 33%
• Platelet count below 150,000/mm3
• Advanced knee osteoarthritis
• Rheumatologic disease
• Chronic kidney disease
• Respiratory disease, including rhinitis, asthma, or chronic obstructive pulmonary disease
• Active or previous oncologic disease, as defined in the protocol
• Fibromyalgia
• Psychiatric disorder currently under treatment
• Substance dependence, including smoking, harmful alcohol use, or other substance use
• Use of nonsteroidal anti-inflammatory drugs within the previous 30 days
• Use of systemic, intra-articular, topical, or inhaled glucocorticoids within the previous 3 months
• Current use of anticoagulant or antiplatelet medication
• American Society of Anesthesiologists physical status classification of 3 or higher
• Currently receiving disability or sickness-related social security benefits
• Inability or unwillingness to provide informed consent or complete the required patient-reported outcome measures