There are only a few reasons a horse may be unable to put weight on a leg.
Non-weight bearing lameness in a limb is one of the most common reasons for a veterinarian to see your horse. It can be quite shocking to find your horse standing with only three legs touching the ground, but often the cause has a relatively easy solution.
There are three main causes for non-weight bearing lameness in horses — a foot abscess, fracture of a bone in the limb or an infected joint.
Of the three, a foot abscess is most common. These abscesses develop when there is infection within the sole or wall of the hoof. The infection can gain entry to the sole through a variety of ways, such as a penetrating wound or infection of the connection between the hoof wall and the sole of the foot — called the white line.
Some horses can develop infection of the sole or hoof via the bloodstream, but this is rare.
When the infection begins, you may not notice anything different about the horse but, usually within about 12 to 24 hours after the infection starts, the horse will not be willing to bear weight. The pain comes from the intense pressure that builds within the sole and hoof wall, as the infection produces a lot of gas and fluid. This builds up pressure as the hoof wall and sole are very hard and do not accommodate any room for swelling of the tissue inside.
Treatment for these abscesses is to relieve the pressure and establish drainages of the infection. This can occur naturally, when pressure from the abscess builds up until the abscess ruptures.
The other option is that a farrier or veterinarian can open the abscess to drain it. This will allow the horse to place weight on the limb again and ensure that the infection can be fully drained and resolved. To help the abscess break and drain, one can soak the foot in warm water and Epsom salts daily. When the drainage ceases, a farrier can place a pad over the draining spot and allow the foot to heal.
Non-weight bearing lameness in a horse is always an emergency as a fracture or joint infection can be life-threatening, but many times the cause is a pesky foot abscess.
Always contact your veterinarian to get the best advice.
Chris Bell is an equine veterinarian and surgical specialist who operates Elders Equine Veterinary Service, with clinics in Cartier and Winnipeg. See www.eldersequineclinic.com