08/26/2016
Interesting
This particular case is a rare lameness. I have probably only seen 10-15 cases like this in my entire career. For that reason, I thought it would be an interesting case to share.
This is a barrel horse who came up out of the pasture with this unusual gait. There was a clump of grass caught underneath a sprung shoe and the mare was off in the left hind.
It is obvious that the mare has a lameness, but there is unusual placement of the hock. On the right hind, the leg bends normally with the hock and stifle flexing together. On the left hind, the stifle flexes normally, but the hock can be manually extended. This is the result of a ruptured tendon in the hind leg called Peroneous Tertius Tendon.
The Peroneous Tertius Tendon originates from the stifle region (distal femur) and inserts in front of the hock. It is part of the reciprocal apparatus, which is responsible for simultaneous flexion of the stifle and hock together. Shown here in the right hind, or normal leg.
The classic diagnostic sign is flexion of the stifle but one can simultaneously extend the hock, shown here in the left hind.
Rupture is due to hyper or overextension of the hock, usually a stall or pasture accident.
Horses are treated with stall rest. Scar tissue forms between the fragmented ends and reestablishes normal function. Most scar tissue has formed in 60-90 days, but maximum strength may take longer. These injuries tend to heal well and most horses return to full work.
Dr. Tanner
