You’ve seen sales clerks wearing wrist braces and computer users with wrist-rest pads in front of their computer keyboards. These devices help protect against carpal-tunnel syndrome, a painful hand condition. It’s often caused by repetitive motion, such as when typing or scanning groceries. It usually starts with odd sensations, tingly or numbness in the hand and wrist but can lead to some loss of use if untreated.
Similar conditions can occur anywhere nerves become irritated within a confined space and swell. The swelling produces odd sensations and/or pain in the areas supplied by the involved nerve.
It’s difficult to diagnose similar conditions in horses because the common early symptoms aren’t something we can see, touch or measure — and the horse isn’t talking. We’d guess these feelings do occur, but aren’t enough to significantly change how the horse moves or performs, except for the case with David.
David was a big, aggressive eight-year-old driving horse with an assortment of minor joint problems. However, he started showing symptoms of a bigger knee problem, winging the leg to the outside in a classical fashion when bringing it forward. He had heat and filling in the lower joint of the knee and a history of knee arthritis, as well as a sizeable old high splint.
An injection of hyaluronic acid quickly resolved the heat and swelling, however, David continued to move abnormally, as if the area still bothered him. The trainer also noted the horse had developed a peculiar new habit of insisting on rubbing his nose along the inside of that knee and the cannon bone after he was worked.
A lameness expert diagnosed a compression of the median nerve where it travels through a tight canal on the inside of the leg. The thought was that the large high splint might be narrowing the space and irritating the nerve, which in turn could be causing him to have odd sensations that triggered the rubbing. Sounds a lot like carpal-tunnel syndrome, doesn’t it'
David was treated by injection in the area of the median nerve and the top of the canal with a mixture of lidocaine, Sarapin and a low dose of corticosteroid. The next day his trot was normal and he no longer was obsessed with rubbing his leg. He was kept sound after this by similar injections every six to eight weeks when in heavy work.
This area on the inside and behind the knee, through which the median nerve runs, is similar to Guyon’s canal at the wrist in people. Nerve compression and irritation in this area is another well-described cause of odd sensations and pain in the wrist/fingers. While problems like this are rare in horses, it pays to keep them in mind when symptoms point to a knee problem but the cause can’t be defined.