This in turn leads to a thickening and widening of the cartilage, thereby providing better protection against injury and degeneration. A joint which is not subjected to any kind of stress, or is not fully used in all possible directions, reacts in an opposite manner, the cartilage thins out and retreats from the extremities of the joint's natural range of motion. It is important to distinguish between joint flexibility and muscle flexibility. Exercise programs for double jointed children must be designed to increase muscle flexibility not joint flexibility Exercises and sports which stiffen joints reduce muscle flexibility, increase compression of the joint, and atrophy the outlying articulating surfaces. Children cannot rely on muscle tension to restrict a joint and the joint will be progressively damaged by the unaccustomed movement beyond its artificially restricted range.
Some people are more naturally supple than others.
Although inherited genes are the usual reason for our physical characteristics, in the interests of evolutionary improvement mother nature will occasionally produce a variation without a family history of a trait. Joints are the junction between two bones the precise shape of the bones defines the natural flexibility of the joint. A shallow socket allows more movement than a deep one. If you have inherited supple collagen you will have supple joints. Cartilagenous bone linings in joints differ in width, thickness and shape changing the characteristics of the skeletal interfaces.