Leg funk on your horse’s cannon bones – it’s cannon keratosis


This leg funk is usually seen on the front of the cannon bone of the hind leg; it’s also known as stud crud. Some folks know this as “urine scald,” affecting all horses, even mares.  BUT…It’s not related to urine at all. This leg funk is also NOT itchy for your horse and is very common to see.


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cannon keratosis leg funk on a horse

cannon keratosis up close on chestnut leg

You will see sticky patches of thickened hair and goop.  It’s scaly, like a hairy lizard.


Stud crud, or cannon keratosis, is a skin condition caused by the horse’s own glands in the skin.


  • It manifests itself in a waxy paste that glues the hair to it. It is not fungus, bacteria, scratches, or caused by urine. It’s a case of seborrhea, which can be primary or secondary. Seborrhea is a flaky and scaly condition of the skin.

But what really is cannon keratosis?


  • In cannon keratosis, the sebaceous glands of your horse go a bit nuts and overproduce sebum. Sebum is that magic skin oil that creates shine. Sebum is also a factor in your horse’s immune system, as it contains some anti-bacterial properties to protect your horse’s skin.


  • If you were to tug at one of those waxy scaly patches, you might pull it out with a clump of hair attached to it. There is a chance that aggressive grooming and picking or other circumstance will leave your horse with some bald patches.


  • If you have some flaky and scaly stuff going on AND there’s swelling, heat, discomfort or hair loss, your horse might have a secondary infection going on. Time to get the vet out.


  • Primary seborrhea is what you find on the hind legs, and isn’t associated with another infection.


  • Secondary seborrhea is associated with skin infection, nutrient deficiency, liver disease, and a few other things. It can also be associated with oily or dry skin.


washing a gray horse's legs

Prescription shampoos from your vet might help.



Your vet can determine if it’s primary or secondary


  • Likely, your veterinarian will be able to give you a special shampoo, probably one that contains benzoyl peroxide.


  • You can also do some things to help, like only using clean and dry sport boots and leg wraps, keeping your horse’s legs clean, and washing and drying thoroughly with your prescribed shampoo.


  • At the end of the day, seborrhea is basically mild, and shouldn’t spread to other parts of your horse, and is very cosmetic in nature.


  • Because the cannon keratosis is just over a bone, I prefer to groom it with grooming gloves and then a soft brush. You can use the same grooming gloves in the wash rack with a mild shampoo to remove the gooey stuff if it’s really bothering you.


  • Some people swear by using that green sheath cleaning goop to soften patches of cannon keratosis, although I have never tried this.


  • Horse socks may also help, these help your horse’s skin be protected from the elements.  Cases of secondary seborrhea and most cases of equine pastern dermatitis benefit from these Silver Whinny socks.  


sox for horses on horse leg with black hoof

The famous Sox for Horses.  And they can get wet and muddy while protecting the skin.


SOX horizontal coupon ad 2023

Remember that loads of horse fungus and skin stuff can look alike.


  • Rain rot, sweet itch, and other skin infections can be distinguished by your veterinarian and the proper medication can be prescribed if needed.  There are tons of reasons horses develop equine pastern dermatitis.


  • Cannon keratosis can be managed through good grooming, but still warrants a look from a veterinarian.


  • Stubborn cases easily causes secondary infections, or if you suspect it’s not cannon keratosis, call your veterinarian and see what’s up!

For a complete guide to leg and hoof grooming, this article has you covered!





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If you need to pick up some fancy-dancy grooming tools for leg funk removal, shop here. As an Amazon Associate, I earn from qualifying purchases, which are not a penny more for you. I couldn’t be more grateful for your support!


horse wearing sox for horses on mat

Sox for Horses for any skin funk, fly problems, summer sores, stomping, and protection from UV light.  Use code PEG23 for a discount on Silver Whinny’s



HandsOn Gloves on horse_.jpg

HandsOn Grooming Gloves – also, use code PEG for some free shipping!


Genuine Cactus Cloth – Natural – 18 X 16-1/2 Standard This is much better for stain removal and spreading natural oils around.

This cactus mitt may be easier to use than a cloth.  

Farnam Excalibur Sheath Cleaner


This shampoo, MediCare, has soothing ingredients for sensitive skin.


thank you!