OCD - please translate!...Ponyvet?

[Zingy]

Can someone please explain to me what OCD is? I know it's something about thickening cartilage around joints, but what does it cause long term (if anything) and what are the chances of it creating a problem?

Thanks

[ponyvet]

If OCD is present then yes it will cause a problem. Here's a very simplified explanation - hope it makes sense!

Bones grow by lengthening at the ends where the joints are. To do this the cartilage grows thick and the ends nearest the joint grow, the parts of cartilage towards the bone become ossified and turn into bone.

The cartilage has no blood supply itself and relies on the joint fluid and the bone beneath to supply all it's nutrients. Now if for some reason the carilage layer becomes too thick (i.e. it outgrows the bone) it cannot get enough nutrients. So the undernourished part of the cartilage dies off. This leaves you with a defect in the cartilage. Eventually this may develop into a flap which protrudes into the joint and may even break off (these broken pieces are called joint mice - dunno why!)

All this happens whilst the animal is growing and so affected animals tend to be young. There are certain places which are moe likely to develop OCD and at slightly different times, as bones grow at different rates. In horses it's usually the shoulder, stifle or hock. You often see swelling of the joint and lameness. The diagnosis is confirmed using x-rays.

In some young horses (less than 2 years old) The problem may resolve if you just turn them out and leave them well alone. However in severe cases surgery is required and the horse will need to have the fragment removed. This does tend to work well as long as the piece can be found. However if the piece is not easily removed the horse may need to be put down.

I have seen cases which do not show up until adulthood - usually this is a horse which has probably had mild OCD as a youngster which probably resolved, but as an adult does some work which strains the already weakened joint - usually in my experience it's a showjumper or a stallion! these may go through surgery and recover too.

The probelm is that even if the horse later seems normal - the joint mouse is removed, or the lesion was found early on and the horse turned away to recover - the defect in the cartilage forming the surface of the joint never recovers. There will always be some sort of a dent in what should be smooth cartilage. As a result the joint surfaces rub against each other and the horse will eventually get arthritis in the joint. Probably when it's still considered to be fairly young.

One of the risks for developing ocd is fast growing big foals. ID, Warmbloods are all particularly prone. There is also thought to be a strong dietary component too - which is why i advise people not to feed their foals on stud cubes, as these are mostly designed for fast growing thoroughbred, and, if fed to a warmblood foal (or ID or similar) will cause him to grow too fast and risk developing OCD. There's also thought to be a genetic link too, so really stallions that have had OCD shouldn't be used, nor if they produce foals which get OCD.

[Zingy]

So if my 8year old has OCD in at least 1 hock (and quite possibly the other as well) this presumably increases the risk of arthritis? He's just been diagnosed as having arthritis in the lower 2 joints which will fuse, but the OCD is much higher in the joint (it actually looked on the x-ray like it wasn't near a bit that moves, but was on the inside/outside of the joint, but this might just be me not knowing what I was looking at). My vet said it could have been the cause of the arthritis (think it's more likely to have been a kick last year that chipped his splint bone), but he wouldn't expect it to cause arthritis in the higher joints. Not sure if he was just trying to make me feel better, so I'd like a second opinion! I'm not sure he should have been that prone to it as a youngster as I think he's a TBxarabxQH, but then I shouldn't be surprised - he likes at least one vets visit a month (think he misses them ). He rarely jumps (poles are scary ) and he's not worked very hard (about half an hour a day flatwork, dresage and hacking). Realistically is it likely that he'll develop further arthiritis? Is there anything I can do now to reduce his chances?

[ponyvet]

He wo;; have been prone to it as a youngster and OCD has to develop when they are young as after a certain age the bones stop growing so by definition it can't form later in life. HOWEVER, as may well be your case maybe he hasn't shown any symptoms so far.

It does sound to me like the arthritis is maybe not related to his OCD. We really don't know how many horses have ocd as youngsters that is never serious enough to cause probelms, since if there is no outside evidence of it we never look. It is occasionally an incidental finding, and may well be with your horse.

In terms of his current arthritis, yes the lower joints should fuse and that will make him feel better. Is your vet going to injet them to make that happen or have you just been told to ride him through it until he gets better? This is because for the lower joints to fuse they need to irritate each other. Youcan either use chemicals in the joint to stimulate this or you keep working the horse in the hope it happens over time.

Either way horses with fused joints (we call this arthrodesis when we do it surgically) can do very well in the long run.

As far as managing him, you can try using a feed supplement like cortaflex, which is supposed to keep the joints healthy and is meant to help prevent and improve arthritis. In addition (or alternatively) you can ask your vet to give your horse a course of Hyaluronic acid which comes in two forms, one that is injected directly into an affected joint, and the other which is injected into the vein and is proven to find its way into the joints. This way will treat all the joints and is probably the best way to use hyaluronic acid as a preventative. however it's not cheap and some vets won't do this for preventative reasons, they like to use it as a treatment.

Hyaluronic acid, by the way, is a normal component of joint cartilage (hyaline cartilage) and so by putting it into the joint you are strengthening the cartilage and it helps inprove the sponginess and smoothness essential for normal joint function.

[Zingy]

He's on steroid injections into the joints. I'm told when these are working he'll be pain free and so I can then work him normally until he goes lame again (or in his case, starts bucking!). He'll then need more injections until the bones completely fuse. I'll ask them about the other injections - these wouldn't cause any problems with wither current treatment or cause any long term damage would they?

[ponyvet]

Depends what you call long term damage - since the steroids destroy the cartilage in the joint and allow the bones to fuse together and that's pretty permanent - LOL!!!

In my experience these horses do well, but you need to be aware that if you try to sell him you must tel any purchaser, as firstly he'd fail a vetting on flexion tests! Secondly it would need to be mentioned on insurance too.