YEP! ME! I have delt with this, and still deal with it with Nelson.
He's a 21 year old TB, whom just started to show issues. He's always been stiff in his hind right, but never showed much to decipher "serious" arthritus. I had him on joint suppliments and thought everything was fine - but just this 2010 Eventing Season, his hind right would "Lock", actually only 2x's throughout the whole season..but 2x was enough.
The first time, we were schooling over 2'11" fences to prepare for an Event that was just around the corner, we were going to sign up to do Novice - and we did a 3 jump combo, I cannot remember the strides....but over the last fence, WHAMO his hind right locked and he landed off of the fence with 3 legs.
The funny thing though, is that he unlocked, and went on like it never happened. I tok him back to the barn though and took care of him, while on the phone with my Veterinarian. I hosed him, rubbed liniment on his hind right hock, buted him and then my vet got out.
We assumed it was a "freak accident" So we started him on Adequan, and he went from a 21 year old, to a 10 year old within the first 48 hours of the first injection.
We did pretty much the entire 2010 season without him showing any signs of concern, and we went on doing our normal routine like it never happened. Until, whamo.....it happened again.
We were schooling again, at 2'11" during a lesson, and his hind right locked, once again.
This time, my vet said "lets get him xray'd" so I took him to the Equine Lameness Specialist - and he did a full examination. He watched him moved and watched for the signs, and asked me alot of questions.
He said "Stiffle"
So we took him inside the clinic, and he palpated him and asked me more questions, then did the xrays. He was actually thrilled to see the xray's. Nelson was shockingly pretty clean, just a bit of arthritus in his hind right hock, the lower is fusing now, which is good.
He then did injections in both hocks, and then he did iodine injections in his stifles. We did 2 bouts of injections in his Stifles.
Nelson is doing great now, we are doing 2'11 without an issue, but of course, I am always keeping a close eye on him.
I took him off all the Joint Suppliments, and just kept him on Adequan. He gets his IM once a month, and come this Spring, before the 2011 Eventing Season starts, we'll get him injections again, even though the Vet said he'll only need them once a year - I just want to make sure he'll be "set".
It is easily managed - make sure you get xrays. Make sure the vet palpates your boy and watches him move.
The stifle sign, is a slight sign - and you can only see it if you are looking. The horses leg stabs down instead of flowing normally. Another sign, is if it feels like your horse trips on his back end. I am not a Vet....just make sure the vet is very thorough.