Optimal saddle fit is the key to equine performance.
Dr Kerry Ridgway made key observations in the relation of the heel height asymmetry to optimal saddle fit. These video convey some key points to consider when evaluating saddle fit in horses with a heel height asymmetry. The larger shoulder tends to exhibit some degree of muscle enlargement while the opposing shoulder appears smaller with a decreased angle. Saddles are built symmetrically so when placed on a horse with muscle enlargement on one side, and rotation of the scapula on the low side, the tree slides over to the low side to find more equal contact. In doing so, the saddle along with the rider is now magnifying the pressure causing pain and restriction of movement. The enlarged shoulder may strike the edge of the bar as the scapula moves that can create significant muscle bruising and further saddle twist. An easy way to check for saddle rotation while riding, try 2 or 3 stops while riding straight, then turn around back to see if your saddle is in alignment with your horse's spine.