I remember that I always wanted to compete, over fences, with my Arabian gelding. Unfortunately, we were advised to give it up because he would cross his legs when he jumped, and frequently stumbled when he landed. We used to always joke that it was because he was from Polish racing stock, rather than jumping horses... but in all seriousness, is there any way to prevent this now or, if your horse does the leg crossing bit, do you have to just give it up as we had to, back in the day?

Theres always a cure. I assume he is crossing from the knees down. That is just laziness. the easiest way to fix this is unmounted. Lets assume he is sensible and lunges fairly well. Set up a grid-gymnastic jumps placed in a straight line. They dont have to be higher than 18"-2'. You may have to adjust distance slightly. Cross rails encourage the horse to bring his front end up,oxers[fence with width]get them to reach and round up,verticles[height no width] rock back on thier haunches. Try settin up in a straight line. A cross rail 12ft to a cross rail oxer- 12ft to a ground pole- 24ft to a single x rail[put the x to one side-high side to leg that hangs lower] 12ft to a verticle 12ft to a xrail oxer. If your standards are low enough, do this off of a lunge at first since you say that he does trip. If he would happen to fall we don't want anyone to get hurt. You may have to ride him though looking at a grid straight on can be very discourageing as all you see are poles and no end and he may not even attempt it.

I agree with what was said - another thing you can do while riding or even lunging him is to set up a cross with poles infront and behind so it's a pole, bounce, cross-rail jump, bounce then pole. Bascially set it up as putting up your cross-rail jump, taking three to four steps out (start off at four, then set it back to three when he becomes more expirenced) and place down a rail from the jump both on the take off and landing side.

Then go through this and slowly raise the sides of the cros from so it gets tighter where he has to jump - this will teach him not to swing his legs, not to drop his legs, not to cross or twist etc etc and put his front legs, and even hind legs, into a better position over the fence.

I had a horse who used to twist and drop a leg something cruel - done that for a while and it "taught" him what position to go over the jump in. And because he got stronger at it and it became easier to jump that way instead of twisting etc

Hope that helps.