Question:
My horse is very sensitive in the flank and the stifle area. When I am grooming her, she seems to get very angry. She puts her ears back and even acts as though she would kick me. When I brush or touch her in the area of the flank or the stifle, she moves her hips toward me and not away. If I push harder, she pushes much harder against me. She has pinned me up against the wall several times and it’s very frightening. What should I do, Mr. Roberts? My instructor says that I should not go into her stall without a whip. I don’t want to whip her, but I don’t want her to hurt me either. There must be a solution to this problem. Can you help me? Sincerely, “Extremely Frightened!”
  
Monty’s Answer:    
Thank you for your inquiry. This is actually a subject near and dear to my heart. This is the pattern of behavior that causes so much trouble with horses in the starting stalls in racing. There are rails inside the stalls which jut out toward the horse. They are there to protect the feet of the jockey but in my opinion, they cause more trouble than they save. The horse that is sensitive in the flanks and stifles will go ‘into pressure’ particularly if its applied to that area of their body. I have maintained for most of my adult life that horses are ‘into pressure’ animals. It is the same phenomenon as we see in the human baby as they bring in new teeth. 
 
The gums are irritated and the child gets comfort from pressing hard on them typically from a teething ring. The horse has survived, in part, because they have learned to go into the sharp pain of a dog biting in the region of the flank. If the horse should run away the dog would simply rip the flesh allowing the intestines to exit the body and the dog makes a successful kill. Survival of the fittest has caused horses to behave with an ‘into pressure’ pattern of dealing with sharp pain. One must use soft grooming brushes on this type of horse and be very careful about staying out of the kick zone. It is essential that we treat this area carefully.
 
You have probably trained your horse to move off pressure without even knowing it. While riding, you will put a leg against your horses side and when the horse moves off the leg, you remove the pressure. You have probably done this on both sides of your horse. Most likely, when your horse was ridden only a few times, there was a tendency to move into the rider’s leg and not away from it. Eventually however your horse learned it was better to move away from the leg. At this present time I have some experiments going on which may prove to be a help with the very problem that you have described. It is to see if we can teach the horse to move off pressure in the area of the flanks. 
 
In order to alter this behavior, I have asked that a soccer ball be attached to the end of a strong bamboo pole. I have asked that the pole be about 6 feet long (2 meters). The ball is actually taped onto the end of the stick, covered with sponge and more tape applied… any way to cause the bamboo stick to be safe when pushed against the horses flanks. I direct the handler to press the ball into the area of the flanks, and stay with it if the horse pushes back. After a few minutes of work, most horses will step away experimenting with how to get the pressure off the ball in the flank. With the slightest step away the handler will remove the ball immediately, releasing all pressure.
 
The reason for the large ball is so that the horse feels no sharp pain. After removing the ball the handler should proceed to the other side and repeat the process. When one can achieve behavior that is immediately off pressure instead of into pressure, you’re well on your way to a successful alteration of deeply imbedded behavioral patterns. Having accomplished this you will be safer to groom, open gates more easily and even have better flying lead changes than you could achieve prior to training your horse to move off pressure even when it’s in the flank area. It is still early in this experimentation, but I think I am the first person to set up this kind of trial. 

After making sure that your horse has no physical ailments, the next step is to desensitize that area. As a point of interest, people who imprint their foals and have aspirations to train them to be performance horses, do not desensitize this area. They leave this area naturally sensitive so that cues can be given by the rider.