Source: Verywell Health
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.