We had a gelding get 2 of those in a pasture accident. Both hocks! I used magnets and compression with vet wrap. Sounds out there, but it worked and he didn't have an indications of them the next year. He was never lame and it never interfered with his showing.
Maybe your vet could give you some ideas on how to work with the swelling, if possible. Also have a letter to submit to the show offices that he is sound from your vet, might help.
Mary S.
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White Rose Ranch
in conjunction with Casa di Vigna Arabians
Home of:
Kailos Halwa (Westwind Pat Hand X Kailos Neblette)
Seleeka (*El Kasaka X Elekaa)
Pocos Golden Boy, ApHC (Aces To Win X Banks Poco Delight)
WR Debbani Farasha (Eclipz Moon Shadow X Zrurik Rajiyyah)
WR Some Like It Hot (pending) (Fire And Ice X Kailos Halwa)
UQH Perago (Unquestionableyhot X KJ Kaneeka (by Karajordge)) On Loan from my grandson, Brenden