The pain inflicted by an ill fitting saddle causes many problems. This pain will become greater as the work is increased and as the rider becomes heavier. Inevitably, this will make the horse unhappy and resent work.
Be aware, though, that there are other, hidden dangers in an ill fitting saddle which can create even worse problems for your horse. This is because when an animal feels pain in one area of its body, it will try to escape this pain by shifting its weight to other areas.
This can twist the body and put the horse out of balance, placing strain not only on the back, but also on the legs, sometimes with disastrous effects.
CAMPBELL THOMPSON - British Equestrian Team Vet for the SYDNEY OLYMPICS explains more:
Horses were not designed to carry people! Over the generations, we have obviously selected those horses that coped best with being ridden but it is still not a natural activity.
Therefore, we have a moral obligation to transfer our weight on to the horse in the most comfortable fashion possible, this means a correct size and fit of saddle for each individual, which allows the horse to still move in a natural, pain free way.
The 'Perfect fit' Kit is a simple, but comprehensive and accurate way for any of us to check the fit of any saddle to any horse and just as important to re-check each season that it continues to fit as the saddle or horse change shape.
Horses are highly sensitive, highly co-ordinated quadrupeds and any pain in one area quickly leads to decreased loading of the sore area and increased loading of the other side or end ie. more weight is put onto hind quarters if front feet are sore. Similarly, if an ill fitting saddle is causing pressure points and pain, the whole back will be held stiffly to limit movement and pain from this source.
A stiff back prevents normal function of the whole core musculature and multiple spinal articulations which increases back problems remote from initial painful area. We commonly recognise sacroiliac pain associated with kissing spines, for example. The reason for this is that the whole axial spine acts as a unit and it is impossible to stop one part moving if it is the source of pain, it is all or nothing, and normal functioning is so important to health of the rest of the musculo-skeletal system. This means that a horse with a sore back from an ill fitting saddle is at significantly increased risk of developing other lameness or poor performance issues, e.g. palmer foot pain from increased concussion on front feet (shock absorber for rider's weight of a supple back- not working) or hock or hind suspensory pain due to the propulsion system having to lift a more dead /less flexible weight.
Therefore, attention to detail with your saddle and saddle fit will have benefits outside purely the saddle area and is to be strongly recommended.