Stem cells are special cells that have the ability to multiply and develop into different types of tissue. In the developmental stages of a fetus, stem cells are plentiful. However, in adulthood, stem cells are restricted to specific tasks of regenerating a few types of cells, such as blood cells. There are not normally stem cells found in cartilage tissue, and therefore there is little capacity to heal or regrow new cartilage.
Source: Verywell Health