I have a 9 year old appendix quarter horse gelding. April of 2011 I was on a trail ride with a friend as we were loping down a trail my horse stepped funny and started cross firing. I couldn't get him to switch his lead so I stopped him crawled off and he was holding his back right leg up to his belly. I had no other choice but to walk him 3 miles home. After 3 weeks off he was sound again, I slowly brought him back And started gaming and barrel racing again everything was good. This past April same thing happened again this time out in a hayfield. He was given time off, brought back slowly. Things were good again, yesterday 7/19 exactly the same thing happened again this time we were on a trail crossing a river with minimal rock that was less than knee deep. When he does this, after holding the leg up to his belly for a few seconds he puts it back down and stomps it on the ground five or six times. His first few steps seem to bother him but once walking it goes away. When he stops again he only let's the toe touch the ground. His muscles look like they spasm in his flank area. I can touch him all over and no reaction to pain. I think it's maybe a stifle problem. It really I'm not sure. Just looking for some ideas or advice...?