My three year old mare creaks and pops when she walks. I didn't see this as a problem, but I've started her under saddle and she seems to have a problem keeping her balance while being mounted. She almost falls over and staggers until she gets her balance. Is this related to the creaking and popping? Is she just being lazy? She keeps one back leg cocked while standing. I don't want to hurt her if this is a medical problem, but if it isn't how do I correct it?