Hi my friends horse has developed a lump at the outside of his hock, when he lifts his leg up it disappears, he isnt lame and it is fluidy, can anyone help to whatit could be, here is a pic of him
Thoroughpin is a distention of the tarsal sheath of the deep digital flexor tendon just above the hock. It is characterized by plantar fluid-filled swellings visible on both medial and lateral sides proximal to the tibiotarsal joint, which distinguish it from bog spavin ( Serous Tarsitis). It is usually unilateral and varies in size. The lesion is referred to as a tenosynovitis of traumatic origin, but it may not be associated with any detectable inflammation, pain, or lameness. It essentially constitutes a blemish and so is of major clinical importance in show horses. Treatment is by withdrawal of the fluid and injection of hyaluronic acid or a long-acting corticosteroid, which may need to be repeated until the swelling does not recur. Radiation therapy also helps reduce the secretory property of the tendon sheath.
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This can also the location for a developing bone spavin. Unlikely if the horse is not lame though and if the swelling disappears when the hock is elevated.
Looks just like a thoroughpin to me. A mare I owned had one just like it, never caused any problem and also seemed to appear overnight. Some of them don't seem to 'push through' when the horse has its full weight on it, try picking his foot up and popping it back down gently on the floor so that it is just resting. Then apply pressure to the lump and see if you can see any movement on the over side of the hock. If it is a thoroughpin you can get a hock pressure bandage from you vet which can help with the swelling, although I gave up as it spent more time around her fetlock than over her hock!