Causes of Enchondroma
An enchondroma is a type of noncancerous bone tumor that begins in cartilage. Cartilage is the gristly connective tissue from which most bones develop. Cartilage plays an important role in the growth process. There are many different types of cartilage in the body. An enchondroma most often affects the cartilage that lines the inside of the bones. It often affects the tiny long bones of the hands and feet. It may also affect other bones such as the thighbone (femur), upper arm bone (humerus), or one of the two lower leg bones (tibia).

What causes an enchondroma?
The exact cause of enchondroma is not known. However, it is thought to happen due to either of the following:

Overgrowth of the cartilage that lines the ends of the bones
Persistent growth of original, embryonic cartilage