A lack of definition between the calves and ankles can occur due to excess body tissues or fluid in the ankles.
In some cases, a person's genetics can cause them to develop naturally larger bones, muscles, and tendons around the ankles. In other cases, having overweight or obesity can cause an excess of fat around the ankles.
Cankles can also occur as a result of fluid retention due to an underlying health condition or situational factors, such as medication use, warm weather, and prolonged standing or sitting.