Horses Back Anatomy
Where you place the saddle is on layers of living tissue, attached to spinal processes and muscles surrounded by fascia, each cell is nourished through circulation and innervated with electrical impulses from nerves within the spinal column.
The collection of these can all be damaged by pressure which is extremely important to consider when it comes down to saddle fit, design and pressure distribution.
Pressure pushes circulation out of living tissue which can damage, bruise and kill cells as there is no longer a supply of oxygen and nutrients. If the area is damaged continuously then the area is replaced by scar tissue.
When nerves are damaged it may cause atrophy (muscles waste away), the horse will lose its healthy top line and develop hollows behind the scapular near the withers giving a hollow look.