Prospective Evaluation of Subchondroplasty in Advanced Knee Osteoarthritis.

Inclusion Criteria: * Patient 18 years of age or older; * Patient with a Body Mass Index ≤35 (BMI=kg/m2); * Patient with Kellgren-Lawrence grade 3-4 Osteoarthritis, as reviewed on MRI and plain radiography; * Patient with knee bone marrow lesions confirmed by MRI result at least 3 months before the intervention; * Patients with degenerative knee pathology at the prosthetic stage (outdated medical treatments), with a frontal deformity of less than 12°, (and wishing to avoid or delay the prosthetic procedure as much as possible) / goniometry); * Patient with unbearable mechanical pain with a walking perimeter limited at 500 m * Patient with non-surgical treatment failure (infiltration of Platelet Rich Plasma (PRP), corticoids, acid hyaluronic); * Patient who agrees to participate in the study and who signed the informed non-opposition form; * Patient physically and mentally willing and able, in the Investigator's opinion at the time of enrolment, to be compliant with the protocol including all follow-up visits, survey completion, weight- bearing restrictions, and post-operative rehabilitation; * Patient with social protection. Exclusion Criteria: * Patient with a Body Mass Index \> 35 (BMI=kg/m2); * Patient with inflammatory rheumatic pathologies; * Patient with frontal deformities (varus, valgus) of more than 12°; * Patient with degenerative pathologies at the operative stage but likely to benefit from a conservative intervention (osteotomy), except if the knee is centred; * Patient with stiff knees (more than 20° of flexum and/or less than 90° of flexion); * Patient with painful severe femoro-patellar osteoarthritis; * Patient with contraindications for Magnetic Resonance Imaging (MRI); * Patient with history of systemic diseases which could contribute to secondary arthropathies (e.g., sickle cell disease, hemochromatosis, or autoimmune disease); * Patient with history of cognitive-behavioural disorders that could interact with assessment by self-questionnaire; * Patient with local or general infection or suspicion of infection; * Patient with severe coagulation disorders; * Patient with primary bone tumour in the knee area, * Patient with undercurrent serious pathology with life expectance \< 2 years; * Female patient of childbearing age that are known to be pregnant during inclusion visit or wishing to become pregnant before treatment; * Patient who has forfeited their freedom by administrative or legal award, or is under guardianship or under limited judicial protection; * Patient participating in another interventional clinical trial or testing an experimental drug within 30 days of inclusion in the study; * Patients who cannot read or write French