Are enchondroma's caused by injury? do they usually grow? how often should they be checked? i have one in my big toe. i'm 57.

Not usually: Enchondromas (a benign cartilage tumor) are usually thought to be from overgrowth of cartilage. They are benign, and don't usually cause problems, especially in a toe. Surgical removal can be an option, but only if your symptoms are bad. If this was discovered incidentally on xray, and you have no symptoms, it will only need to be checked periodically by your doctor (usually yearly).