Functional Brain MRI to Understand Pain Phenotypes in Knee Osteoarthritis

Some people with knee osteoarthritis (gonarthrosis) experience pain differently. In some, the pain is described as "nociceptive" (directly related to the joint), while in others it has "neuropathic" characteristics (related to nerve function). The goal of this multicenter, cross-sectional and comparative study is to compare resting brain activity in a brain region called the anterior insula among female patients with painful knee osteoarthritis who experience nociceptive pain compared to those with neuropathic pain. Researchers will compare brain activity at rest between these two types of pain in women over 40 with painful knee osteoarthritis. A better understanding could help improve pain management in the future. Participants will be asked to : * complete questionnaires during the inclusion visit and on the day of the scan, * undergo a clinical examination and a blood test at the inclusion visit, * undergo a functional MRI (fMRI), an imaging test that allows observation of brain activity at rest. Paticipants in the study does not involve any additional treatment. the fMRI scan is non-invasive and does not require any injections.

Inclusion Criteria: * Women aged 40 or older (only women will be included to ensure consistency in the analyses, given the higher prevalence of osteoarthritis in women and the influence of sex/gender on the experience of pain) * Diagnosis of femorotibial osteoarthritis of the knee according to the 1986 American College of Rheumatology criteria * Presence of knee pain with an intensity of ≥ 4/10 on a numerical rating scale (NRS) * Chronic knee pain, i.e., lasting at least 6 months with at least 15 days of pain in the past 30 days * Completion of the PainDETECT questionnaire, which will allow the patient to be assigned to one of two groups prior to the enrollment visit (those with nociceptive pain \[score ≤ 12\] and those with neuropathic pain \[score \> 13\]) * Patients have read and understood the information letter * Patients have signed the informed consent form * Patients are enrolled in a social security program Exclusion Criteria: * Other joint diseases affecting the knees (gout, chondrocalcinosis, rheumatoid arthritis, spondyloarthritis, psoriatic arthritis) * Conditions that, in the investigator's opinion, interfere with the assessment of osteoarthritic pain, such as conditions causing neuropathic pain in the lower extremities (e.g., peripheral neuropathy, chronic radiculopathy) or fibromyalgia * Kellgren-Lawrence radiographic stage IV in one or both knees * Patients with one or more knee prostheses * Claustrophobia making MRI impossible * Contraindication to MRI * Pregnant or breastfeeding women * Patients under guardianship, conservatorship, deprived of liberty, or under judicial protection * Patients who have participated in an interventional clinical trial within the last 6 months that could impact the primary endpoint