Crossing of hind legs / Stifle

Question
We have a 25 year old Saddlebred mare, who up until about a month ago was completely health. She started kicking out at the canter with her left leg and it was determined that she was locking her stifle. About two weeks ago she started crossing her left hind leg over the right at the walk. She doesn't seem to be doing it at the trot or canter, but she trips at the walk and the trot (not at the canter) so her back end kind of falls. She has stopped kicking out at the canter so I am not sure if this is related to the stifle or not. Do you have any idea what may be causing this?

Answer
Dana:

Stop riding her. She is 25 and needs to do nothing more to earn her keep. she could have some osteoarthritis, she could be getting a touch neurologic, she could be getting too weak to be able to continue to support a rider and work on the flat. She could now be dangerous to herself and to the rider. She's 25 and in my opinion, should live out her days eating nice grass and enjoying life. The diagnosis in my opinion is not made here, but is also not relevant for a 25 year old horse that sounds like shes done her share for you. Let her be a pasture ornament and let her eat and enjoy the rest of her life- in my humble opinion. My best to you and your extraordinary mare. Please let me know if I can help you in any way.