Inclusion Criteria:  Knee osteoarthritis Kellgren-Lawrence grade 2, 3 or 4 . Chronic painful knee of mechanical characteristics. Absence of local or systemic septic process. Hemacytometric and biochemical analysis without significant alterations that contraindicate treatment. Written informed consent of the patient. The patient is able to understand the nature of the study. NEGATIVE serologies: Syphilis, HTLVI-II, HIV, Hepatitis B virus (HBV), Hepatitis C virus (HCV) and HCV PCR (must be repeated if more than 30 days elapse between its completion and the extraction of bone marrow in patients to whom autologous cells correspond). Body Mass Index 20-35 Kg/m2.  Exclusion Criteria:  Patient < 18 years old, or legally dependent. Patient > 75 years old. Congenital or evolutive diseases that result in malformation and/or significant deformities of the knee (varus<10º; valgus<20º) that cause difficulties in the application and evaluation of the results. Pregnant or breastfeeding women. Neoplastic disease. Intra-articular infiltration of any drug in the 3 months prior to inclusion in the study. Concurrent participation in another clinical trial or treatment with another investigational product in the 30 days prior to inclusion in the study. Allergy to gentamicin (antibiotic used in the cell culture process). Other diseases or circumstances that may compromise the participation in the study according to medical criteria.