The sources to obtain Mesenchymal Stem Cells are very different, some of them are: bone marrow, adipose tissue, placenta, umbilical cord and endometrial tissue, which due to its unique properties has been the subject of study of many doctors. These properties include its low invasive level, its regeneration level, its capacity to isolate a great number of cells from little tissue and its capacity to be easily obtained through a biopsy. Cartilage is one of the tissues of the body whose regeneration rate is low, mainly because it is poorly vascularized and due to its function it is very susceptible to trauma and inflammation, besides its cellular matrix has a very complicated structure that is difficult to mimic. One of the most common degenerative diseases affecting cartilage is osteoarthritis, which decreases the life quality of the people who suffer from it, causes pain and can be disabling. In general, there are many factors that can damage cartilage, including weight, age, gender, genetic factors, physical activity, etc., and the most commonly damaged joint is the knee. Among the therapies known to treat osteoarthritis are thick fluids (called viscosupplementation) that simulate the extracellular matrix of chondrocytes (cartilage cells) to cushion the friction between bones that cause pain and slow cartilage degeneration. However, this treatment does not stop the destruction of the cartilage and does not stimulate its regeneration. Therefore, a viable alternative has been explored using the transformation capacity of the Mesenchymal Stem Cells (MSCs). Although the most researched MSC´s so far come from bone marrow, other sources such as endometrial tissue are drawing attention due to the properties mentioned above. These cells have the ability to differentiate into chondrocytes to form functional cartilage, but they also help decrease inflammation in the joint and therefore stop the death of chondrocyte cells. In various pre-clinical studies carried out on rabbits, mice, horses and other animals, its effectiveness in the regeneration of cartilage and recovery of functionality has been proven. The translation of these results into a clinical study is currently underway, but it has been described that it is possible to reduce joint pain, increase the ability to move and even walk, and repair damaged tissue to some extent. So far, the creation of cartilage from Mesenchymal Stem Cells is still in an experimental phase and requires special care to ensure that the differentiated cells do not return to their original state and remain functional for the time required by the patient. Another promising alternative is the use of 3D bio-scaffolds to be placed on the patient’s joint and filled with stem cells so that they can differentiate in vivo and create the lost cartilage, both treatments are not yet routinely available worldwide due to their complexity. However, it is widely known that Mesenchymal Stem Cells secrete in a paracrine way, growth factors (VEGF, EGF, FGF), chemoattractants and anti-inflammatory cytokines (IL-10, IL-13) that can be used as a source of bioactive molecules with the ability to modulate the metabolism of the cartilage extracellular matrix as well as to promote angiogenesis and the proliferation of Mesenchymal Stem Cells in a specific tissue. Therefore, the application of Mesenchymal Stem Cells directly into the joint is one of the therapies that has shown so far the most results in the clinic. The combination of the application of MSC in the joint with medication (hyaluronic acid or Platelet-rich Plasma) is a decision directly made by the treating physician since the appearance of the patient, level of physical activity, degeneration, diet and hereditary factors that could interfere must be taken into account. Thus, it is important to go to an expert so that the treatment is adequate. Bibliography: Uzieliene, G. Urbonaite, Z. Tachtamisevaite, A. Mobasheri, and E. Bernotiene. (2018). The Potential of Menstrual Blood-Derived Mesenchymal Stem Cells for Cartilage Repair and Regeneration: Novel Aspects. Stem Cells Int. 2018: 5748126. doi: 10.1155/2018/5748126. Freitag J, Wickham J, Shah K, and Tenen A. (2019). Effect of autologous adipose-derived mesenchymal stem cell therapy in the treatment of acromioclavicular joint osteoarthritis. Case Report. BMJ Case Rep; 12(2): e227865. doi: 10.1136/bcr-2018-227865 Park MJ, Moon SJ, Baek JA, Lee EJ, Jung KA, Kim EK, Kim DS, Lee JH, Kwok SK, Min JK, Kim SJ, Park SH, Cho ML. (2019). Metformin Augments Anti-Inflammatory and Chondroprotective Properties of Mesenchymal Stem Cells in Experimental Osteoarthritis. J Immunol. pii: ji1800006. doi: 10.4049/jimmunol.1800006.