Assessment of the Effects of Chondroitin Sulphate in Patients With Knee Osteoarthritis With Functional Magnetic Resonance Imaging (fMRI)

Inclusion Criteria: * Primary knee OA according to ACR criteria * OA of radiological stages 2 to 3 according to Kellgren-Lawrence * Estable knee pain during the last months before to start the clinical trial * Patients with pain as the VAS≥50mm at baseline Exclusion Criteria: * Patients with skin conditions that could interfere in the clinical trial evaluation * Pregnant or breastfeeding woman * Patients with a history of alcoholism or other drug abuse * Patients with an uncontrolled active psychiatric disorder * Patients with other inflammatory or systemic conditions affecting other joints * Patients who suffer more intense pain in the joint in another location * Patients unable to differentiate between symptoms caused by the knee in front of the joint study opposite * OA of radiological stages 1 or 4 according to Kellgren-Lawrence * Other bone and articular diseases such as chondrocalcinosis, Paget's disease, rheumatoid arthritis, aseptic osteonecrosis, gout, septic arthritis, ochronosis, acromegaly, hemochromatosis, Wilson's disease, osteochondromatosis * Patients with contraindications to perform an MRI such as: certain tattoos, pacemakers, intracranial clips incompatible with MRI, in the heart valves, hearing aids and other types of implants are incompatible with MRI * Known allergy to chondroitin sulphate * Washout period for OA treatments before beginning the study