The primary objective of this study is to identify osteoarthritis (OA) structural changes, as assessed by MRI, that best correlate with the presence of neuropathic pain (NP) using the PainDETECT questionnaire (PainDETECT ≥ 13) on a population of patients with OA of the knee experiencing moderate to severe pain (VAS ≥ 40 mm).

This study is a multicentre, cross-sectional observational pilot study. The presence of NP was determined based on use of the PainDETECT questionnaire (score 1 to 38), the score of which was defined for the purpose of the study as ≥ 13. A total of 50 OA patients with moderate to severe pain (VAS ≥ 40), 25 without the presence of NP (OA/NP-) (PainDETECT score < 13), and 25 with the presence of NP (OA/NP+) (PainDETECT score ≥ 13) were enrolled. Since this is a pilot study, we arbitrarily determined the number of patients at 50, which represents 25 patients per arm, a number deemed sufficient to identify the knee OA structural changes that could be preferentially associated with NP.

Inclusion Criteria:

• Individuals of either sex, aged 40 years and more;
• Followed in an ambulatory clinic;
• Presenting with primary OA of the knee according to American College of Rheumatology (ACR) criteria;
• With an OA of radiological stages 2 and 3 according to Kellgren-Lawrence;
• Knee pain for at least 1 month out of the 3 months preceding the study;
• Visual Analog Scale (VAS) of pain while walking on a flat surface ≥ 40 mm;
• Agrees to sign the Informed Consent Form;
• Not taking part in another clinical trial;
• Agrees to respect the protocol.

Exclusion Criteria:

• Other bone and articular diseases (antecedents and/or current signs);
• Presenting with isolated knee lateral compartment OA defined by joint space loss in the lateral compartment only;
• Knee surgery on the study knee;
• Comorbidities that restrict knee function;
• Had received any investigational drug within 30 days or 5 half lives (whichever is greater) prior to entering the study;
• Unable to give informed consent;
• Counter-indication to an MRI examination;
• Baseline Visit cartilage volume cannot be calculated from the MRI due to advanced OA or any other technical reason;
• Abnormal findings and or any other condition, which, in the Investigator's judgment might increase the risk to the subject or decrease the chance of obtaining satisfactory data through MRI to achieve the objectives of the study.

Presence or absence of neuropathic pain on a population of patients with OA of the knee experiencing moderate to severe pain (VAS ≥ 40 mm)