Hock injections: pros & cons

The horse hock is a very complex joint. This joint actually consists of four separate joints. The uppermost joint (tibio-tarsal) is the one that is most commonly afflicted with OCD. OCD (osteochondrosis dissecans) is a condition in which a small flap of cartilage is unattached from the bone. This condition causes swelling, lameness, and can lead to arthritis. OCD is usually diagnosed in young horses and is treated with arthroscopic surgery. The prognosis is usually excellent.

The next joint down is called the proximal intertarsal joint and it communicates with the upper, tibio-tarsal joint. Problems in this joint are not as common. If problems do occur, an intra-articular injection is the treatment of choice. The medication can be put in the top joint since they do communicate.

The remaining two joints which are the lower of the four are named the distal intertarsal and the tarsal-metatarsal. These are the two joints most afflicted and treated in the sport horse or athletic horse. In athletic events such jumping, dressage, reining, roping, and many other activities, these joints undergo a lot of stress. Stress on these joints causes inflammation which can then cause pain.

Pain involving the lower two hock joints can manifest itself in many ways. Some examples include shortening of the rear leg stride, lead change difficulties, and change in ability or willingness to jump. Abnormalities involving these joints may also manifest as lower back pain. Back pain develops secondarily when a horse alters his stride due to hock pain.

How are these conditions treated?

Ask 10 different veterinarians and you will get 10 different answers.
Here is a list of the many modes of treatment;

  1. NSAIDs: Anti-inflammatories such as Bute, Banamine, Equioxx.
  2. Oral supplements: chondroitin, glucosamine, MSM
  3. Systemic medications: IV Legend, intramuscular Adequan
  4. Intra-articular medications (joint injections): usually consists of a drug called hyaluronic acid and a steroid

We are going to focus on the intra-articular injections. First, let’s discuss the drugs we inject in the joint and what they do. Hyaluronic acid (HA) is a normal component of joint fluid (synovial fluid). Injecting HA into the joint will decrease inflammation and promote healthy joint fluid and articular cartilage. The steroid we usually also inject is a very potent anti-inflammatory. Decreased joint inflammation equals less pain and better performance results. Decreasing inflammation will stop the cascade of events leading from inflammation to arthritic changes. In addition, an antibiotic is usually mixed in with our cocktail to decrease the risk of a joint infection secondary to the injection.

Hock injections are taken very seriously by me and our clinic. It is not a procedure without some risk. If a post injection infection were to occur it can be difficult and expensive to treat. Because of this risk we prefer to do the procedure in the cleanliness of our clinic. The horse is heavily sedated, the site of injections are clipped and prepped as if for a surgery. Strict sterile procedure is followed. This includes sterile equipment, surgical gloves, and strict sterile techniques. A total of four injection sites are used, i.e. the lower two joints of each hock. Following injections, we clean the site of blood and spray with an antibacterial spray.

The horse following injection is usually given that day off. The following day a light workout is suggested. After that, the horse returns to normal exercise. The frequency of follow up injections or treatment is decided on a horse by horse basis and the animal’s response to the injections. If you have questions about this procedure, please call, I will be happy to consult with you.

Todd Welsh, DVM