Understanding Your Rope Horse's Hock

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What the Hock Is and What it Does
The horse's hock is at once it's most powerful and vulnerable joint. A horse that can use his hocks well-and therefore hindquarters-can run faster, jump higher, pull harder and stop quicker. But if a horse's hock is hurting, his performance potential plummets. And, unfortunately, because the hock is such a complex joint, there's a lot that can go wrong. First, it's important to understand what the hock is and how it works.

The hock, or tarsus, is the complex joint in the equine that allows quick locomotion and durability for the rope horse. This is the joint that allows the hind legs to quickly flex forward in the stride to prepare the quadriceps to powerfully propel the horse as the hocks extend.

The anatomy of the hock is complex. To begin, the tibio tarsal joint is the highest joint and responsible for most of the movement. It is lubricated by synovial fluid that is produced and maintained by the articular cells that line the joint and protect the underlying bone.The synovial fluid is also responsible for absorbing concussion forces as the weight is distributed over the joints.

Next, there is the proximal and distal intertarsal joints, which also may share some of the synovial fluid in the higher joints. The lowest joint in the hock is the tarso metatarsal joint and usually possesses its own joint fluid, which may not communicate with the others.

The durable joint capsule suspends the joint fluid in each respective joint space and it is important to have a good quality fluid in order for protection and efficiency.Although the lower three joints combined only account for 5 percent of the total motion of the hock, they are responsible for a substantial amount of the problems in the horses going up and down the road.

This complex joint is surrounded by a host of important blood vessels, ligaments, nerves and tendons.There are no muscles around or below the hock in order for the tendonous structures to maneuver the distal limb. The digital flexor tendons pass through and over the inside and back part of the hock, and are critical in supporting the horse's weight. The Achilles (gastrocnemius) tendon runs down the back of the limb above the hock and attaches on the point of the hock. If this tendon is cut, the whole function of the hock is lost, the hock folds, and a horse cannot support any weight.

The horse is built so the stifle, hock, fetlock, and foot move in unison.This allows the horse to rest while one leg is locked and is also instrumental in the performance horse's ability to create powerful, concentrated propulsion.

Common Hock Problems in Rope Horses
The rope horse is a unique individual. Most rope horses are broke to be ridden and then tried and tested to see if they can achieve the speed, agility, and heart it takes to become an exceptional athlete.Whether they are bred for specifics or simply stumble into the sport, genetics play a vital role in the conformation of the horse and specifically the hocks. If a horse displays poor rear limb conformation, the hock joint will be affected later on in life.What's more, when a horse becomes stressed and tired, his muscles, joints, and other soft tissue structures become vulnerable to injury.

Straight hocks are ideal and allow the joint wide range of motion with a moderate amount of wear and tear. Solid conformation also affects the flexor tendons, suspensory ligaments and hoof angles. The cannon bone should be perpendicular to the ground, the hock joint straight when looked at from behind, and slightly angled when viewed from the side. Both hind legs should be symmetrical with no obvious swellings.

Sickle hocks and cow-hocks, on the other hand, are less desirable traits when looking at a performance rope horse. For horses that stop or turn dramatically, such as calf or heel horses, long cannon bones may also pose unwanted stresses on the hocks.

A rope horse in pain or discomfort will often swish his tail and shut down or come out of his stop. If a horse exhibits this behavior, it is important that a veterinarian perform a thorough spinal exam and incorporate a lameness exam. Hock flexion tests and passive lameness tests (Churchill Spavin Test) are imperative while watching the horse on a hard surface in a straight line and a circle to help establish the severity on exam.

Although most of the movement is in the high joint, most of the problems in rope horses are seen in the lower joint spaces. There is where lesions, referred to as degenerative joint disease, most often occur. They are either traumatic or worn injuries, which over time lessen the degree of performance.

More often than not these early signs go undetected or poorly diagnosed. Swellings of the joint capsule or a boney enlargement on the inside of the hock are often the first noticeable signs. By this stage there is inflammation in the joint capsule, degeneration of the joint cartilage, and remodeling of the underlying bone

Your vet should know that it is common for a horse to have muscle strain in the para-lumbar musculature of the spine from overcompensating for sore hocks. What's more, bone spavin, bog spavin, thoroughpin and capped hocks are other rule-outs involving the hock and related structures. One common injury that shows similar symptoms to distal tarsitis is suspensory desmitis. This lesion shows similar clinical signs, blocks sound occasionally on a lameness exam and is confirmed by ultrasound. This lesion carries a much less favorable prognosis and sometimes requires up to a year's worth of rest.

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Current Therapies and Preventative Measures for the Hocks
Veterinarian examination is a must when lameness or back soreness is suspected. Without proper diagnosis, treatment and time, the horse may be put into jeopardy by further injury. Make sure you tell your veterinarian the kind of work your horse is doing, as well as the frequency. Baseline radiographs, a thorough lameness exam with diagnostic nerve blocks and proper interpretation are important when establishing a diagnosis, prognosis and treatment plan. Further tests that may be needed include an MRI, CAT scan, ultrasonography and nuclear scintigraphy.

Once the diagnosis is confirmed, a plan needs to be established. Acute injuries may go undiagnosed and the source of pain may be the only thing established, still a recheck should be performed before the horse goes back to a normal workload. Proper rest for any injury is vital to a healthy recovery. Many horses are overworked, resulting in further injury, when one more week would allow a better recovery.

Special considerations should be made to determine which option is best for your horse. The 15-year-old practice horse that spends five days in the practice pen and makes 100 runs a week should be taken care of at a high level due to the mileage. He will need a good warm up and cool down. If he feels good in the practice pen, you will be able to concentrate on improving your game. If he is hurting, you may develop bad habits and decrease his longevity. Your plan for the horse that only goes to one or two rodeos or ropings a month should be different. Since he has more time in the pasture between events to recover, and if he is conditioned and warmed-up properly, his chances of injury are minimized.

There are many different regimes used today for protecting the articular surface and improving articular function. Oral nutraceuticals come in many forms and contain many products. These products are good for healthy joint maintenance and providing the body with some necessary additives that the horse may not be deriving from his diet. These compounds are usually a daily maintenance given orally.

Stronger forms of glucosamines are available for injectable weekly or monthly therapies. Systemic Polysulfated Glucosaminoglycans (PSGAG) are commercially available for labeled use to treat damaged cartilage. They may be injected intravenously, intramuscularly, or intra-articularly. This product is designed to strengthen the articular bond at the cellular level, which protects the surface of the joint. This, in turn, allows the cells to produce a high quality synovial fluid by working more efficiently.

Intravenous and intra-articular use of hyaluronic acid (HA) also is instrumental in providing a better quality synovial fluid, which protects the vulnerable articular cells. These products work differently to achieve a similar goal and, therefore, they are often used in combination. When intra-articular therapy is begun, different types of combination therapies are used with steroids. Some are long acting and others short acting. Steroids combined with the HA seem effective due to the protective function against the steroids, however, long term use of corticosteroids in the joints may impede the ability to heal.

Often, non-steroidal anti-inflammatory drugs (NSAIDS) are used daily to reduce the pain and also used in combination with rest for recovery. These are generally oral or injectable forms such as phenylbutazone, flunixin, and ketoprofen, but topicals such as diclofenoic acid and DMSO are valuable as well.

Many cases of distal tarsitis involving the lower joints will resolve because the joints fuse together, minimizing the movement and damage. There are also surgical techniques and intra-articular therapies that can aid in the fusing of the joints. The current use of IRAP (Interleuken Receptor Antagonist Protein) intra-articularly, stops the inflammatory cycle. These proteins are harvested from the plasma and injected weekly for several treatments. This is particularly beneficial in the younger horse in the beginning stages of degenerative joint disease, who has a bright future in the arena.

A thorough understanding of the severity and prognosis should be the basis for a practical treatment plan for each case. Rope horses are used as much as any athlete and hauled more than most horses, so owners must maintain their joints to ensure their longevity in the arena.

Conditioning and Strengthening for the Rope Horse
In today's sport of rodeo, competitors must have a consistent warm up routine for their equine athletes. Because there are more rodeos to go to, different arena conditions, different climates, and all the travel these stressors play important roles with regard to injuries and fatigue. Injuries and fatigue are instrumental in decreasing a horses' performance level and will directly affect longevity of the horse.

As a horse is exercised, the circulation increases the body temperature and allows a wider range of motion for the muscles, tendons and ligaments. This allows the vital structures more flexibility, thus reducing injuries such as avulsions and torn ligaments. In addition, the muscles can work more efficiently, which works as a temperature regulatory mechanism by allowing the horse to perform at a lower body temperature and improving stamina.

The most effective warm-up routine is symmetrical exercises in both directions at a walk, trot, and lope. Off-day exercises are vital. Long trotting during the week will help achieve full potential when done on a routine basis-three or four times a week for 20 minutes. Rope horses should also perform similar warm ups at the rodeos or ropings. After a few weeks of a normal routine, you will see your calm horse pick up a little and your high-strung horse knocked down a notch.

Hill exercises improve the quality of the hind limb musculature, which will protect the hocks and place the stress away from the joints in the healthy horse. Lunging in both directions on the side of a hill or long trotting up the hill, then zig-zagging back down at a walk or slow trot is a great exercise. Do these 20 minutes a day and you will see improved rear limb function in the hock as well as the stifle.

Finally, cooling the horse down will minimize the stress and allow healing after demanding performance. The lactic acid build-up will dissipate better, allowing the horse to feel better the next day and minimize stiffness. By slowly incorporating the warm up, cool down and conditioning/strengthening patterns, your horse will improve his athleticism.