Almost everyone has heard the three-finger rule for saddle fit: that you should be able to fit three fingers between the withers and the pommel of the saddle. But do you know why? It’s more than just protecting the nerves and muscles that run down your horse’s back, the saddle also needs to leave enough room for full range of motion of the scapula. The construction of English saddles can block the scapula if there is not enough room, otherwise, the muscle will atrophy over time and your horse will become sore.
In general, fitters recommend a 2-3 finger width between the withers and the pommel. A saddle with a tree that’s too wide will sit too low in front, causing pressure on the withers. One that’s too narrow, or with a too-narrow gullet, will pinch and put pressure along the sides of his spine. The number of fingers is less important than evaluating whether there’s enough room. I’ve had saddles that I thought fit a little low, but my horse was very happy with the fit and he was the ultimate arbiter. I’ve had other saddles that looked like the fit just fine, but the horse moved short until I changed the saddle.
Horses that have flatter (mutton) withers will often end up with more room (or need a hoop tree) and horses with more pronounced withers may have less room (cut back saddle designs can help).
For proper fit, it’s important that the front of the saddle are parallel to the angle of the horse’s back at the site directly beneath the tree points. In addition, you should position the tree points two inches behind the scapula to account for the “normal” scapular range of motion of two inches.
To make sure the saddle does not hinder the backwards movement of the shoulder blade and allows enough room at the top and at the side of the withers, position your hand sideways, not flat, under the pommel to see if there is enough clearance over the horse’s withers.
This video from Schleese provides good information on how to evaluate whether your saddle fits your horse. Please also keep in mind that what’s most important is how the saddle fits with a rider in it. Sometimes it’s not going to be three fingers; two fingers is fine. It just needs to have enough room.
What’s your experience with saddle fitting? How many fingers fit under your saddle?