Horse Illustrated Magazine

The hock is a hind limb joint that is fundamental to your horse’s movement. Read on for the five most important things you need to know about this complex joint.

What’s the big deal about hocks?

Your horse’s hocks, anatomically called the tarsus, are the equivalent of our ankles. One of the most complex joints in the body, the hock works to extend and flex the hind limb and acts as a major shock absorber.

The hock is made up of four smaller joints that work as a unit. It contains six bones, a host of extensor and flexor tendons, collateral ligaments, and an Achilles tendon.

What can go wrong?

The most common problems encountered with hocks are due to two things: conformation and stress from use. Horses with poor hind-limb conformation, such as those with sickle hocks or those that are post-legged, naturally place undue stress on the hock joint.
Horses that are put into demanding work without proper conditioning and adequate recovery during training likely will face hock issues. Sometimes it’s a combination of these two factors.

The two most common hock problems in the horse are bone spavin, also called distal tarsal osteoarthritis, and bog spavin, also called tarsocrural effusion. The degenerative joint changes seen with bone spavin can be seen on X-rays, and horses with this chronic condition are usually lame to some extent.

Bog spavin is a result of long-term, low-grade inflammation within the joint, causing increased production of joint fluid. Horses aren’t always lame as a result of bog spavin, but the hock will appear swollen. A veterinarian can drain the swelling, but it is likely to return if the underlying reason is not addressed.

How can you maintain healthy hocks in your horse?

Reducing concussive injury and battling inflammation are the two primary ways to help your horse’s hocks stay healthy. Maintaining adequate and regular hoof trimming can help ensure your horse’s lower leg is in the best alignment possible, which helps decrease stress on the hock.

Proper conditioning is crucial to prepare a horse’s hocks for demanding work. Adequate rest after workouts is also essential. Twenty-four hours between workouts is enough to allow for acute inflammation to subside in most cases; keep this in mind during competitions if your horse is scheduled for more than one event per day.

After hard workouts, consider cold therapy for your horse’s hocks. This is a very simple and effective way to reduce immediate inflammation after a workout. Cold-water hosing or ice wraps applied immediately post-ride for 15 to 30 minutes is sufficient and can help reduce soreness.

What about oral supplements for joint health?

Oral dietary supplements for joint health usually contain one or more of four main ingredients: glucosamine, chondroitin sulfate, methylsulfonylmethane (MSM), and/or avocado-soybean unsaponifiable extracts (ASU). Other ingredients may include hyaluronic acid (HA), devil’s claw, grapeseed extract, yucca, garlic, and vitamin C.

These products are designed to help manage arthritis and promote a healthy joint environment. Consult with your vet if you think your horse would benefit from an oral supplement.

These types of oral supplements have been around for a long time, and the veterinary community recognizes that the top four ingredients (glucosamine, chondroitin sulfate, ASU, and MSM) are considered safe for horses. The choice to use a supplement is a cost/benefit analysis for each individual horse owner.

If you decide to try an oral joint supplement, be an informed buyer. Research the brands and read the labels. All ingredients should be listed on the label along with the amount of active ingredients, which can vary widely by brand. Check to see if feeding instructions are clearly described.

As a rough guideline, an average adult horse should receive 12 grams of glucosamine hydrochloride or 15 grams of glucosamine sulfate per day; 2.4 grams chondroitin sulfate per day; 2,100 mg ASU per day; and/or up to 10 grams MSM per day. Also look for manufacturer information on the label; if this is not clearly listed, do not use the product.

Options when there’s a problem

Intra-articular joint injections of corticosteroids and hyaluronic acid are a common method for managing a horse with chronically inflamed and/or arthritic hocks. Corticosteroids are strong anti-inflammatory agents and hyaluronic acid is a synthetic joint fluid that helps lubricate the joint directly.

Joint injections are not a cure for hock pain, but provide short-term relief. They are commonly used as part of a maintenance program to keep horses comfortable during work. It should be noted that joint injections are not without risk; occasionally, infection can be introduced into a joint through the needle. However, if strict hygiene is followed during the procedure, this risk is minimized.

Frequently, joint injections are used in combination with systemic NSAIDs such as phenylbutazone (bute). The long-term use of NSAIDs can be detrimental to a horse’s health, particularly his stomach and kidneys. But there are newer NSAIDs available, such as firocoxib (Equioxx), that have less potential to do damage.

Other injectable joint therapies given either in the muscle (IM) or in the vein (IV) provide more options for hock health. Legend is the brand name for hyaluronic acid that is given IV. This product is designed to increase the quality and quantity of joint fluid.

Polysulfated glycosamingoglycan (Adequan) can be given as an IM injection; this product is intended to strengthen joint cartilage and stimulate the joint to produce more joint fluid.

A more aggressive therapy for chronic hock problems is joint fusion. This involves surgically fusing the lower joints within the hock. These joints don’t contribute much to the motion of the joint, but do contribute a lot to inflammation. Once fused either surgically or naturally with age, these joints no longer rub together, thus lessening or eliminating pain.

Caring for your horse’s hocks requires an individualized plan based on the horse’s intended use and conformation. There are many options for both prevention and treatment of painful inflammation and damage. Working closely with your veterinarian to discuss options will help ensure your horse’s hocks are managed in the best way possible.

Anna O’Brien, DVM, is a large-animal ambulatory veterinarian in central Maryland. Her practice tackles anything equine in nature, from Miniature Horses to zebras at the local zoo.

This article originally appeared in the June 2016 issue of Horse Illustrated magazine. Click here to subscribe!