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

The goal of this randomized clinical trial is to learn whether taking ibuprofen, a nonsteroidal anti-inflammatory drug, after a platelet-rich plasma (PRP) injection changes pain relief and knee function in adults with knee osteoarthritis. The main questions it aims to answer are: Does ibuprofen change the improvement in knee pain six months after a PRP injection compared with acetaminophen? Does ibuprofen change knee function or the need for additional pain medicine during follow-up? Researchers will compare PRP followed by ibuprofen with PRP followed by acetaminophen. Participants will receive one ultrasound-guided PRP injection and take the assigned medication every eight hours for five days. They will complete assessments of pain, knee function, additional pain medicine use, and safety. Participants and the physician performing the injection will not know which medication was assigned.

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