I was called to work on a horse that had a mystery lameness in the hind leg. The chiropractor and farrier were both puzzled by the discomfort the horse was demonstrating. He looked very stiff in the hock area, and I wondered if maybe he needed hock injections, as he is in his teens. I found an area of tightness and proceeded to work gently, as the horse flinched when I touched the muscle, which is the peroneus tertius.
This muscle extends the hock and flexes the stifle simultaneously. After a few minutes of massage and cross fiber friction, I had the owner walk him out. He looked better, and I did another round of deep pressure massage. This muscle is very stringy and tendinous, so can easily become tight. It is not naturally a pliable spot on the horse. Massage in the area of the peroneus tertius and gastricnemius is good insurance against such a build up of tightening and stress that a rupture is unavoidable.
The owner has reported that her gelding is moving normally and returning to light work. I will be returning for another treatment very soon, as this is an area that takes several sessions to improve.