Horses: Weird lump on Fetlock *vet out*


12 Years
May 29, 2007
New York
I noticed my mare has developed a weird lump on the back of her fetlock joint (on/near the Sesamoid bones?). While she is standing, it's hard, almost bone-like feeling, but when her foot is lifted, the mass has a slight 'squishy-ness' around it.

There's no heat or swelling. It doesn't hurt her and she is sound on it.

I am still lightly riding her, while riding I keep her legs wrapped or booted, and there hasn't been any problems... I'm just concerned as to what it may be. No one at the barn has any ideas; the farrier will be out Tuesday afternoon so I will ask him about it then, but still.... it's just weird.

At first I thought she accidentally kicked herself, but it's been a week and there's no change. Then I thought freak-bone spur, but it's perfectly round and the 'texture' just doesn't seem right to be that.

Anyone have any ideas?





[^^^The lump is rock hard, not puffy or bubbly.]

* NOTE: Her pastern/fetlock isn't swollen (even though it looks to be in the pic) and yes, the farrier is coming out in a few days.
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Maybe a non-cancerous carcenoma. we have a mare on the farm that is up by her head...its not a problem for her as long as it stays kind of squishy and's more cyst like, really.

I'm just throwing out a random thought........
No, there's nothing... no cut/scratch/ or puncture. It's just a hard round bump/lump about the diameter of a nickle (5 cent piece).
This is not an ergot we're talking about, is it? If so there should be a more or less matching one on the back of the other fetlock of the pair. (I don't *think* that's what you're talking about, but as it is a hard nubby thing on the back of a fetlock, just thought I'd check...)

So, three questions.

1) is the hair/skin affected in any way (is there a crusty or warty or bare area, or anything like that) or does the lump appear to be solely underneath the skin, with the skin and hair appearing totally normal?

2) where exactly is this located. Is it on the vertical surface of the back of the fetlock, or on the 'back corner' sort of where the ergot would be, or on the underside of the fetlock as the horse is standing?

3) is it exactly central (when viewed from behind) or is it off towards the inner or outer side of the fetlock.

Some possibilities that come to mind would include "a harmless bump from a hind foot", a small tendon-sheath injury from a bump/misstep, a tendon injury (they're not always obviously lame), sesamoid issues (the bones themselves or the bursae etc around them), or inflammation of the annular ligament; but there are about a zillion other possibilities too, especially if the skin and hair *are* affected.

Your farrier can probably offer a sensible opinion on whether it's worth a vet call, but as it is also fun and educational to play "I wonder what that is" on the internet, I would be happy to take a whack at it too if you want to give more info

Good luck,

Thanks Pat.

As I have said, it's not bothering her at all, so I'm continuing to exercise her [with precaution]. At first I thought she might have overreached and kicked herself, but it has been a week and there's no change in the mass (it's not 'healing or getting worse for that matter'). I was also thinking it was a freak/large bone spur, but that doesn't quite feel right and I was also leaning towards tendon/ligament sheath injury, but I would have expected that to be more of a soft/"bubble" feeling rather than rock hard... so I'm at a loss.

I have been looking online and asking around and haven't found much on what it could be expect came across a list of "fetlock joint 'diseases' and have been weeding out possibilities...

[the list I found:]
* Fracture
* Fracture/luxation
* Avulsion injuries of the proximal sesamoid bones
* Disease of the proximal sesamoid bone
* Osteoarthrosis
* Osteochondrosis
* Schematic drawings of fetlock fragments
* Villonodular synovitis
* Ischaemic bone necrosis
* Bone cyst
* Osteomyelitis
* "Epiphysitis"
* Diaphyseal angular deformity
* Puncture wound
* Osselets
* Granuloma

I just hope it's nothing too serious... Again, it's not bothering her any, but I do worry about her. This mare is just getting back into condition after a [hind] suspensory ligament injury that she endured 16 months ago; she NEVER had any health or soundness issues prior, but now it's been one thing after the other with her, so I'm a little paranoid...

I'm sure my farrier will have more of an idea, but you're welcomed to guess if you like, lol.
^^^ no... windpuffs and thoroughpins are soft.

[She does have windpuff, being an ex-reiner that was started too young
, but this mass is definitely not one of those...]
^^^ No - no heat, no pain, no lameness...

I'm on my way there now to work with the baby (3 yro), so I'll try to take a pic of it.

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