When examining a saddle tree closely anyone would find that it's very hard and rigid, usually. In a typical English saddle for instance, the tree is frequently made from wood and steel. When the rider stands in the stirrup to mount-up, the pressure from the rider's weight transfers up the stirrup straps which pulls the tree downward, driving the tree parts into the horse's shoulder.

From the horse's perspective, do you think they would ask you for a tree that bears into their back every time you stepped-up into the stirrups? Probably not. If your horse walks away from you when you try to mount it, picture how that tree is driving into your horse right behind the scapula. The horse begins walking away to get away from the pain.

If at some time, you switch from a treed saddle to the treeless saddle, you may find that the horse still walks away from you when you mount-up. It's likely that, that shy-away action was learned from the previous saddle's digging and you'll have to give your horse some time to re-learn that being mounted doesn't have to be painful. It's my bet that the horse's predicament was probably never taken into consideration when it came to building saddles around hard, inflexible trees.

Have you ever had a saddle that slid-up on the horses neck? The news is that the saddle didn't really slide ... the horse pushed it there. When the horse works the muscles in it's back end, it's hip and leg muscle groups push on the back of the saddle. And because a tree is rigid, the saddle gets forced forward onto your horse's neck. With the treeless saddle, it flexs around, and the saddle doesn't get pushed forward.

The problem with trees is that the bars of the tree do not conform to the curve of the horse's back. The equine back constantly changes with age, physical condition and of course when in motion. It moves because of the muscles and bones moving around laterally or vertically as the back flexes up and down or when turning. The combination of the motion and the curves result in a bridging affect where the bars of the tree arch over the back's curve leading to excessive pressure on the front and/or rear bars. Sore backs for horses occurs most often because the bars of a rigid tree often bridge the natural curve of a horse's back leading to excessive pressure under the front and/or rear bars. Attempts at shimming and using specialized pads to make an ill fitting treed saddle fit better has not been helpful in most cases. In addition, the trees often add little pressure points, and bars that extend beyond the pommel and cantle can easily create rubbing problems on short-backed Arabs, Icelandic, or Paso Finos breeds.