Tensegrity. Tension + integrity. This describes the structural integrity of the body - yours and your horse’s. We can no longer think of joints as surfaces that wear out over time; as surfaces that are pressed together when loaded held apart by incompressible fluid - that is not accurate. Tension in muscles, tendon, aponeurosis, fascia situated away from the joint creates space in the joint. The entire system balances tension forces. What we think of as wear-and-tear is repetition of excessive unbalanced tension in soft tissue. When damage progresses beyond that, then you can have reduced joint space and possible contact - this is extreme and extremely painful and lameness is usually there before this. We want to address the imbalance, the overloading way before we have this much damage; at the earliest signs of discomfort. The imbalances are observable and fixable.  The word "Stretchy" when describing horses' gaits is ambiguous and can lead training in the wrong direction. The elasticity we want to feel when riding is that of an efficiently balanced tensegrity system which mean there is the appropriate orchestration of muscle tone, not muscle relaxation. When we ride a horse, our tensegrity system combines with the horse's tensegrity system and therefore there is a responsibility of the rider to find the balanced tensegrity that enables the horse to be efficiently balanced.  This is the key to soundness in both horse and rider.