Fusing hocks - can someone explain in layman's language.

I have never understood this phrase “hocks are fusing” or “fused hocks”. Is this basically arthritis in the hocks?

I heard that all or most horses get hock arthritis eventually. How serious is this? Can it be treated so the horse can still be used and/or shown.

I also heard that some horses fuse at different times. Some horses don’t ever have fused hocks even if they are very old.

And how do vets handle this in prepurchases. Do they just call it “fusing hocks”, arthritis?, remodeling? degeneration? or ???

Is it a deal killer in buying or selling a show horse.

I am so confused about this!!!

Thank you for any and all input.

Here’s a good start with visuals of the hock joints, which I find helps a lot:


It’s all osteoarthritis, proper management over a lifetime (footing, workload, farrier care etc.) can slow it down but they all generally get it, as do we humans. Possibly a genetic component as some families may be more affected then others.

There is no “cure”, no majikal supplement to give to prevent it. Just treat the symptoms-stiffness and pain.

Far as the fusing, the dummies version is within each joint and the spine, bone surfaces that mesh together are seperated by a pillow of cartilage. Over time, the pillow deflates and the bone surfaces meet directly as they move and cause pain.
Joint injections relieve that and help the cartilage plump up but only temporarily.

Eventually the space closes up as the cartilage wears away so that bone moves againt bone with no cushion and that’s referred to as fused. Sometimes they surgically fuse joints and vertebrae to speed up that process as it reduces the pain greatly. Unfortunately it also reduces the range of motion within the joint so performance is generally affected negatively.

This is generally called “Arthritic changes” on a PPE. Deal breaker? Maybe, maybe not. 12 year old schoolmaster, been there done that going well in the job buyer is looking for? Probably not going to disqualify it but buyer needs to be aware it will need to be managed with joint injections as well as things like Pentosan, Legend, Adequan plus the good management mentioned in the first line of this post. If the joint is already fused, no injections into the joint will do anything, the needle doesn’t even have a space to go into.

Young horse, horse largely inactive like sitting in a field for years or one that’s never been in a serious training/work programming with arthritic changes? Most buyers will pass. It’s one thing to keep a hard working older horse comfortable and able to work. Quite another to commit to years and years of expensive treatments on a horse thats never learned to do a job knowing it was not miles of hard work that caused the early deterioration of the joint.

Hope this helps you out with fusing and joint deterioration somebody else can tackle remodeling, OCD and the finer points.

Great explanations so far!

One thing I’d add, OP is that the “fusion” everyone is talking about is in the lower (distal), low-motion joints of the hock. The joint space in there is quite narrow to begin with. You can inject the top, high-motion joints of the hock. But that’s not where you start, and vets usually would prefer not to.

As findeight has described, these big, heavy animals we ask to work create inflammation in the cartilage and synovial lining of their joints. The synovium (tissue) responsible for making that lubricating joint fluid gets irritated and then it makes less-healthy joint fluid… and so inflammation continues…and so the cells in the synovium create worse joint fluid and so on.

That cascade screws things up and one of the main reasons people put chemicals like steroids and/or Hyaluronic Acid into joints. Both help interrupt the inflammatory process. Steroids have some drawbacks as far as their effects on tissue/HA is expensive.

All this is to explain what anyone is doing when they are injecting hocks (typically). And that relates to your question about fusing hocks because people 1) are referring to those narrow, low motion, lower joints of the hock; and 2) injecting those joints if great precisely because you don’t care if they fuse.

As you can imagine, the process of fusing, ruining cartilage until the horse is bone-on-bone but before those bones have knit together, is painful.

And back in the bad old days of yester-century before intra-articular injections were routine, the cure was to bute the horse and ride, ride, ride until that hard work sped up and completed the fusing process.

Anecdotally, I think there’s probably a heritable component to whether or not and when a horse’s hocks fuse. And I think that relates to bone metabolism and irritation-- whether or not the horse with angry soft tissues at the margins of his joints lays down a lot of new bone or does not. That’s because you can see horses with horrific X-rays that are clinically sound or who haven’t worked that hard. And you can see horses who have worked hard with X-rays that are remarkably clean. I suspect that horses in that latter group have some genetics that make them not go crazy with producing new bone… or they have stout, toleration synovial tissue and cartilage. If we can’t genetically engineer horses like that, we should treasure these animals as breeding stock. There’s no other cure of equine osteoarthritis.

Here’s a good start with visuals of the hock joints, which I find helps a lot:


BTW, the horse’s hock is homologous to the human ankle joint. So if you can’t figure out which joints move a lot and which don’t, look at a picture of the human foot and appreciate the joints that are ahead of your ankle and form the instep of your foot. Those are the “lower hock joints” that we’re talking about.

Really great explanations thus far IMHO.

I will reiterate that sometimes, it is our goal to see a hock fuse because in some cases that decreases pain, improves stability, and once through that process, a horse is sound and not painful.

But in many cases, the reason a horse ends up in that position to begin with is due to overuse injury or other injury so certainly not something you’re “looking for” out of the gate.

Depending on the intended use for a horse, a fused hock would not necessarily be a deal breaker for me at a certain age if the horse were in work and sound with that condition.

However, if I were looking for a performance horse and not a trail riding buddy, it would certainly give me pause and cause to look further into the medical history and soundness history.

I think that some people have gotten to the point where they’re pretty flippant about arthritic changes in joints and IA injections and fusing. I am probably a bit more conservative. It has been my personal experience (being careful not to point to others here) that this is typically something that was caused by overuse and thus, if affecting one part of the body, is likely to have caused issues elsewhere that may not have surfaced yet but will be more problematic in time.

Because I tend to be a “this is your last stop” kind of horse owner, if I were shopping for a horse right now to do what I want to do (dressage, eventing), I would probably skip over a horse with known joint issues because I can only have one horse at a time. I know what the down stream management can look like from a mental and physical health standpoint for the horse and for owner’s pocket book. Wouldn’t hesitate to lease a horse with this though if the horse were comfortable.

A fusing or fused hock generally means the two lower bones, those that provide one way motion up and down, why a horse can have “fused hocks” there and keep working fine.

Not so with the upper bones, those are needed for sideways motion and if those have problems, the horse won’t be able to move comfortably.

X-rays will tell so much of the story.
It depends on what is seen there how the vet may evaluate the horse for future use.

Two years ago, I vetted a horse that I had ridden on trial for a week. 12 year old. He had been good as gold, and I liked him. I was 62 and looking for a solid sane 2’6" horse.

The vetting showed an old injury to his hock, which made it arthritic. X-rays showed that it was about 60% fused.

My vet was not happy, but I told her my bones were more important than his, and bought him.

He gets a yearly checkup with hock injections, but more importantly, he is a love and did not disappoint in the "good horse’ department.

He just had a yearly checkup and the hock is about 85% fused now. Vet say another two years until 100% fused.

I really don’t see a lot of ill effects. He is a little stiffer on the left lead canter (it is his left hock), and I give him monthly Pentosan, but he is worth it by far!

I think it needs to be clarified that “arthritic changes” and “joint fusion” are NOT the same. They’ve been used interchangeably, in day to day and in this thread, but they are two separate processes.

Arthritic changes is the eventual deterioration of joint spaces due to stress on joints over time. This is the “bone on bone” scenario findeight mentioned. The cartilage wears over time until you start getting bone on bone contact, which usually is very painful. Most horses don’t make it to “bone on bone”.

Fusion is the process of two bones becoming one, a process which happens because the body is essentially saying “this joint is unstable, we need to stabilize it”, so it actively attempts to calcify the joint space so the joint essentially becomes one solid bone. If we are talking hocks, it is almost always either the tarsometatarsal or intertarsal joints that fuse. These are the lower two joints out of the three that make up the hock. These two joints have very, very limited mobility, and fusion, if it occurs and finishes, generally doesn’t tremendously affect the horse’s ability to do a job. However, active fusion is very uncomfortable for the horse, and you see folks taking all kinds of measures to make the horse more comfortable and keep them rideable.

Fusion of the highest hock joint, which is highly mobile, would likely result in euthanasia, as it would cripple the horse.

Fusion is actually not terribly common. Arthritic changes are pretty common as horses get older. It’s part of the natural aging process, and can vary from severe and career ending to completely manageable.

^^ :yes: :yes: Except there are FOUR joints in the hock. :smiley:

^^ :yes: :yes: Except there are FOUR joints in the hock. :D[/QUOTE]




A prior vet of mine told me that he always injected all three joints, while most vets only inject the upper 2 when “injecting the joints”. I understand
in general what he meant, but now you say there are 4 joints? hmmmmm Now I am really confused.

And can someone explain why some vets only inject the top 2 joints while others inject 3?

[QUOTE=Lord Helpus;8614888]
A prior vet of mine told me that he always injected all three joints, while most vets only inject the upper 2 when “injecting the joints”. I understand
in general what he meant, but now you say there are 4 joints? hmmmmm Now I am really confused.

And can someone explain why some vets only inject the top 2 joints while others inject 3?[/QUOTE]

You should never inject the “upper” joints of the hock. Only the lower two joints. The top two joints communicate though so you can inject one and it would go to both.

The standard joints to inject are the tarsometarsal and the distal intertarsal joints.

I’ve got some great article that I share with my clients who have questions about hock pain, fusing hocks, etc… I will upload them to my dropbox and share them here. It maybe a few hours as I’ve got to head into work but I should have a break mid-day.

^^ :yes: :yes: Except there are FOUR joints in the hock. :D[/QUOTE]

If you want to get technical, yes. :yes: I was lumping the proximal and distal intertarsal joints into one.