We have a jumper with a box foot, as well as a dressage horse whose sire throws known club feet. We don't worry so much about the dressage horse, just maintain a good farrier.
The jumper on the other hand, we actually have some trouble with the other foot. This horse is 12, shows monthly, sometimes twice a month. He stays sound and competitive. The other foot gets under run, and should have some additional support, and it's toe will get sensitive.
I think it is imperative to get a baseline, and your vet on board if you plan to compete over 3'. A boxy foot on the outside does not mean the structure is too far off on the inside. However, you may have a really wonky angle in there and you risk damaging your suspensory.
We had a hunter with a mild club foot, she was a very nice mover, top in the hack. We had trouble keeping shoes on her clubed foot and unrelated soundness issues. We do think it contributed to a bad bad crack in her hoof though.
For a moment there, you bored me to death
Well, every case is different but as I tell my clients it's like having a car that has 18" rims on three wheels and a 17.5" rim on the other wheel (or whateverever number one uses with respect to cars). Sure, the care is going to run fine but over the long haul that slight uneveness may throw the car's suspension or frame (or whatever) out of whack and could possibly result in problems.
Of course there are all degrees of club feet from imperceptibly mild to a stump-like appearance. And then you find that horse with 4 perfect feet, vets perfectly clean, take him home and the next day he colics severely and dies....
Talk with your farrier. My Adult Eq/Jumper was an intermediate eventing horse (no little jumps there!) and he has a slight box foot and it never bothered him there. We were told it was a club foot so when he was getting vetted, I had the farrier come out and look at it. My farrier is absolutely awesome so if he told me he could keep the horse sound, then I had no worries. Horse vetted great and shows 3-3'3" once or twice a month and does travel to clinics, etc. He shows 3'6" with the pro and we have no (knock on wood) foot issues. With a good farrier, a slight club, dished, box foot shouldn't be an issue as long as the rest of the horse is sound.
Just as an FYI, horse is 16-year-old thoroughbred who came out of the eventing world at 15 due solely to being bought by me; not a soundness issue. Though, he will probably last longer doing the little AA stuff with me!
Had a 3'9" jumper with a club foot for over 5 years. Never had an issue to date. Kept farrier schedules on time and that was it. Never had a day lame. Just consider that some vets when doing a PPE might not approve a horse for purchase because of a club/box foot...
Over what hill? Where? When? I don\'t remember any hill....
My mare is a bit clubby on one foot. (Knock on wood) it hasn't slowed her down at all and I haven't ever had an issue with it. (Shhhh, don't tell the horse gods I just said that, because you know how they are!) She is 9 and has been showing the 1.30-1.35 this year and schools over 1.45 at home. We don't jump high very often, but that is just good horsemanship, not due to her feet.
Mine has a club foot! He's not sound right now, due to recovering from OCD surgery, but his whole life he's always been just fine with his one clubby foot!! Xrays clean now that the OCD's are out and needs corrective shoeing due to soft feet (stall rest post op causes that frequently) but always alright on that club foot.
I've worked with 3 different horses with varying degrees of clubbed feet in my lifetime, and thinking about all of them to this day I am slightly blown away by the engineering of all three horses because they were all sound, sound, sound.
One horse was a very successful Grand Prix jumper with the slightest of clubs - I believe there was some disagreement if it was a true club or not but the angles were unusual; one was a successful A rated A/A hunter with a fairly bad club, and one was an all-around eventer/Pony Club/beloved lesson guy who in his 20s was still blasting around x-country on 2 of the ugliest club feet I've ever seen - no problem.
The jumper and the AA hunter were managed impeccably by some of the top farriers in the country and had long, SOUND, and (in the case of the jumper) brilliant show careers.
The PC/lesson guy was equally well-managed by a less well-known local farrier and again, I do recall he was ridiculously sound, which I distinctly remember because his angles looked so deformed, like stumps!
Personally my instinct is to run away screaming from anything that has a club foot but then I think of these horses (and the current wonderful racehorse Lisa's Booby Trap!) and figure maybe with proper management it ain't the worst thing in the world!
Maybe not totally what you're looking for, but my AO hunter horse came out of the jumper ring where he was a year before I bought him and lord knows how long in Germany before he was imported and he has a club foot and we don't have issues with it, but it does seem to matter who is shoeing him--people who try to get all fancy on it cause it to bother him/throw more shoes. He just likes a solid shoe job on it and nothing too tricky. He's 12, showed consistently in the 4' and the 3'6" divisions for 4 years and now mostly just does the 3'6". I never worry about the club foot, just make sure to keep bell boots on him as it's more prone to losing a shoe.
Back in the early 90's, I purchased a 3yr old OTTB filly with a club foot. She was by far the best jumping partner I've ever had the privilege to ride. At about age 12 she started to go "off" and never recovered. I believe she had Lyme looking back at her symptoms and it was not due to her foot (Lyme was unheard of back in the day). Such a shame...her mind still wanted to work but her body couldn't keep up with it.