Odd horse- why does he do this?

[charlie76]

My horse has a really odd habit. When you touch him on the inside of his hind leg on the near hind at the bottom near the coronet, he snatches it up and waves it at you. He does this when you bandage near this area and if you wash this leg. If you touch anywhere else on the leg, he is fine to touch, its just that one spot. Bizarre.
He is 100% sound, fine to shoe and has no wound or injury. He did have the smallest mud fever scab in that area about 2 yrs ago!

Any suggestions?

 

[Nari]

Probably not relevent but one of mine does this if he wants the inside of his thigh or sheath scratching. He looks like a giant dog cocking his leg up a lampost!