Your horse's boots might not strike you as a very complicated piece of tack, and because of that their fit is often overlooked. We use boots to protect the horse's legs, but using them improperly can result in damage from the boots themselves, injuries from areas not covered by the ill-fitting boot or discomfort for the horse.
I have written previously about the different types of open-front boots (see post here) and this post will outline how to fit a pair of boots as well as the common mistakes that riders make when putting them on.
A correctly-fitted boot should be just shorter than the length of the horse's leg from the bottom of the knee to the bottom of the fetlock. The boot should cup the fetlock (if you are using a moulded plastic boot, ensuring that the fetlock area fits is especially important to prevent rubs), fit snugly up the cannon bone and then finish below the bony projections at the side of the knee. This keeps the boot from rubbing against the knee while at the same time giving the knee room to bend, which you'll need over the jumps!
The straps should be tightened so that they are just snug. You should still be able to squeeze a finger between the strap and the boot (your horse's leg will change shape slightly during each movement so you want to allow some give, and also let the blood circulate through the skin).
This is how a front boot should fit:
This is an example of the same boot (therefore the correct size for this horse) placed too high on the leg (unfortunately the knee and fetlock are not very clear because the legs are black):
This photo illustrates why there should be room left at the top behind the knee. Even with the cut-out section at the back, the boot pinches the skin at the back of the knee when it's partially bent:
Short open-front back boots are easier to fit since the length isn't a problem, but fastening the straps so close to a joint can be tricky because it's more difficult to hold the boot together with one hand while you do up the straps with the other. For that reason, the easiest way to put on a pair of back boots is by fastening them first over the cannon bone (loosely) and then sliding them down into place.
You'll get a feel for how tightly to fasten the boots after a few tries. Because you aren't fastening the boots in their proper location, it's extremely important to check the final tightness every time you apply them because it's very easy with this method to over-tighten a boot by making it snug around the cannon bone. Always slide the boot in the direction of the hair growth; there's no need to slide them upwards before taking them off.
- Boots that are too big: If the boot is so long that it runs up into the knee and extends past the bottom of the fetlock, it is simply too big and you need to try a different size or brand of boot. Nothing you do will make it fit properly.
- Straps that are too tight: I see this more with boots that use buckle or stud closures because sometimes they need to be overtightened to reach a hole, which is one of the reasons why my personal preference is for velcro closures. Velcro can, however, also be over-tightened. If an indent is left on the leg after you remove the boot, or if you cannot squeeze your little finger under the strap, it's too tight. Open-front boots shouldn't need to be over-tightened to prevent them from slipping down the leg because the shape of the leg should prevent the boot from slipping if the straps are comfortably snug.
- Boots placed too high: As seen above, boots that are too high can rub and prevent the knee from bending without pinching. Some boots might slide into place during the ride while others might stay too high, depending the the particular boot, leg and tightness of straps.
- Boots placed too low: Putting the boots too low on the leg leaves the back of the leg with less protection from the back hooves and runs the risk of rubbing the fetlock if the narrow part of the boot meant for the cannon bone is placed there. The straps can also lie over the fetlock joint if they are too low.
- Boots falling off: This can be a problem with velcro boots on horses that have a lot of knee action. An easy solution if you wish to continue using velcro fastenings is to apply a layer of Vetrap around the boot over the closed velcro. Use Vetrap that matches the colour of the boot and wrap it no tighter than the fastenings on the boot; it can even be a bit looser because it is just there to keep the two sides of velcro from separating to the point of fully detaching.