My family recently bought an 8 year old Quarter Horse gelding. I know very little about his past other than he was a 4H project for a young girl and did western pleasure. He's now been turned into a hunter. He does a little bit of everything from trail riding to being a beautiful jumper. He's a very quiet guy and I've never had any problems with him on the ground. I have noticed that he's a little stiff and less willing to bend tracking to the right. I was injured a few months ago and in order to keep him moving I started working with him in the round pen. Every time I asked him to go to the right he would spin and come running right at me bucking and kicking. Obviously this is dangerous so I stopped working in the round pen because I wasn't physically able to get after him. I left for college so I have not worked with him since and my mom has been riding him with no problems.
I'm looking for some input as to what this may mean. The fact that he is stiff to the right under saddle makes me think this may be him responding to pain. But his stiffness is nothing more than what I've felt in most horses who have a favorite direction or lead and my mom says he has gotten much better. Is it something I should have a chiropractor look at? Or is this a training issue. The horse can be lazy and at first I thought it was just him trying to get out of work. Any input would be much appreciated.