AAEP Convention 2001: Lameness in Horses

There are many lameness problems that are associated with the use of a horse in a specific discipline, or the conformation of horses selected for use in a discipline. However, there are some problems that are universal, and the diagnosis and treatment of those problems will follow similar lines.

Following are presentations and discussions from various veterinarians who make their living working with horses who perform for a living, whether in the rodeo ring or on the trail.

Lameness in Rodeo Horses

Rodeo's popularity is increasing throughout the world. The physical demands place on rodeo horses are strenuous, said Bobby Lewis, DVM, president of Elgin Veterinary Hospital in Texas and a past president of the AAEP. The many hours trailering between  events--coupled with the varying climates, arena surfaces, and arena sizes--cumulatively create stresses for these athletes. "Almost any lameness is possible," Lewis said.

Just like other performance events involving horses, there sometimes is a fine line to be drawn between lameness vs. suboptimal performance.

"Videotapes can be of valuable assistance--a practical substitute for actually witnessing the horse perform," explained Lewis. "Videotapes played in slow motion can actually be more helpful than watching the horse perform."

He said practitioners should use caution in interpreting findings, particularly in older rodeo horses. "These horses last a long time and go a lot of miles, so you will see radiographic changes that don't have clinical significance."

While understanding that point, Lewis uses flexion tests and hoof testers to determine areas of pain. He reminded the audience that with these tough-footed rodeo horses, hoof testers must be capable of exerting sufficient pressure to get a response. "You have to remember those older rodeo horses are more stoic and it's harder to elicit a pain response," said Lewis.

Diagnostic anesthesia is essential in confirming sources of pain. "Many horses have multiple sources of pain. Sometimes you don't realize you have secondary sources of pain until you get primary sources blocked or under control," he said. Lewis recommends having the horse ridden with diagnostic anesthesia because not all problems can be seen with the horse in-hand.

He stressed again that veterinarians should use caution when interpreting radiographic findings, particularly in older horses. "This is especially true of finding bone spurs. If your findings are suspicious, it is best to confirm radiographic findings with diagnostic anesthesia. The signs of wear and tear are expected in these horses, especially since many of them will work until they are 20 or older."

Sport Horse Lameness

Rick Mitchell, DVM, IVAS, works with upper-level jumpers on the East Coast, and Kent Allen, DVM, has a referral clinic in Middleburg, Va., that caters to upper-level eventers. They both are private practitioners who have worked with the world's best horses and riders. "Rick and I have the same problem," said Allen. "By the time we see the horse, several vets have already had a go at him, and you are not going to resolve the horse's problem in 15 minutes with hoof testers. So, you need to go more rapidly to a higher level of diagnostics."

The two led a discussion on sport horse lameness evaluation during a lunchtime session.

Mitchell, who is board-certified in veterinary acupuncture, said he uses acupuncture points as an evaluation. "It is not a stand-alone diagnostic, but neither is radiography or ultrasound," he commented.

Allen said that in his practice, he first does a thorough history, especially looking at the horse's feet. "It's easy to see if the horse is poorly shod, but if the horse is well shod, you don't know if his feet are part of the problem or not."

Allen likes to use thermography. "One of the wrinkles is that if you are going to use a thermograph, then the horse has to come in without wraps or a lot of dermitis on its legs," said Allen. "Conversely, if you want to use thermography and you've already blocked the horse, you've lost your chance for a while."

Mitchell said, "When you are evaluating subtle performance problems, a real issue for me is that a lot of horses are sent in with hocks and stifles injected, and backs worked on, and acupuncture and chiropractic done, and the horse is still not doing right. The first thing I do is put gastroscope in these horses.

"I published a paper where I found that 63% or greater of performance horses have gastric ulcer problems," said Mitchell. "When some horses are not performing well it might not be lameness. There might be some other physical issue."

Western Pleasure Horse Lameness

As the veterinarian for the large Lazy E Ranch in Oklahoma, Joe Noble, DVM, MS, sees lots of different horses used for different disciplines. He said a Quarter Horse used for pleasure classes should have free-flowing gaits, be fit and balanced, and cover a reasonable amount of ground in his gaits. "Their gaits have been changed by man," said Noble of the slow-motion movements now winning in the arena. "Whether you like it or not, these guys (trainers) are not going to change the way (the horses) move."

Noble said that he fights a battle every day in which owners and veterinarians are over-diagnosing problems in these pleasure horses. "I don't like to inject the hocks if the horse isn't having visible problems, but sometimes I will inject them and the horse gets better. It doesn't correlate well with clinical signs," said Noble.

A new development in the way the horses are used that probably will result in lameness problems is that riders are starting to lope horses on a diagonal along the rail so the hock doesn't flex. "This is bad for the horse," said Noble. "I'm not sure how the AQHA going to address this. There is going to be a higher amount of distal tarsal inflammation in these horses."

Noble said he thinks veterinarians overlook foot lameness in pleasure horses. "It seems the wider the shoes and pads, the better we like them," he said. "These horses aren't genetically designed to have a good foot to start with."

He said pleasure horses often are reset to "change way they go, and we drive too many nails into marginal hoof wall they have. Veterinarians and trainers make the farrier's job almost impossible. There are a large number of horses that come to major events that have acupuncture points injected and hocks injected, and in the afternoon they mysteriously have a foot abscess going on. To me, the foot is the place to sort out on these pleasure horses."

Suspensory Ligament Injury

A room full of practitioners attended the lunchtime table topic on suspensory ligament problems moderated by Van Snow, DVM, of Santa Ynez, Calif., and Larry Bramlage, DVM, Dipl. ACVS, of Rood and Riddle Equine Hospital in Kentucky.

Snow said that addressing the feet and giving "mechanical advantage" back to the horse is usually an immediate relief to these sore horses. He said he has had very good luck using shock wave therapy.

"If I can see core lesions (in the ligament) using ultrasound, then I tell the owner he's out of luck for a quick fix," said Snow. "If the alignment of the fibers (in the ligament) is out, then the horse can possibly train through it."

Snow said the he likes to keep horses in some degree of fitness during treatment because once the horse  starts getting sound, the trainer gets in a hurry to get "caught up" in training and the horse can be hurt more seriously.

Bramlage said that in the late 1980s, he did a project looking at the strength of the suspensory apparatus. Using dissected suspensory ligaments on a machine in the laboratory, he found that the strength was greater from horses in active training than from those which had been stalled or just living in a field.

In discussing shock wave therapy, Bramlage said, "We've had some pretty good luck and colossal failures." He said it seems to work better if the lesion is primarily within the bone and not within the suspensory.

"Some horses get surprising pain relief and go on to train fine. I still don't know the answer (why this happens)," continued Bramlage. He said veterinarians question whether the shock wave therapy  acts as a temporary neurectomy (deadening of the nerves). Both veterinarians said there are various types of machines out there, which don't all work the same.

Both veterinarians said they have seen transient analgesia from electromagnetic therapy. They cautioned its use because of this effect. "You can't be sure the horse will stay structurally intact if you use it (therapy) right in front of exercise," said Bramlage. "I saw a nice horse that broke a cannon bone when he had a known stress fracture and wore an electromagnetic boot up to race time. That was the last race of his career."

Electro-Acupuncture for Lameness

More and more studies are being done to determine the effects of alternative therapies in veterinary medicine. In a study presented by Huisheng Xie, DVM, PhD, MS, of the University of Florida, during the Dolly Green Lecture Series, it was determined that acupuncture might help reduce lameness through the production of beta-endorphins.

Researchers at the University of Florida used six Thoroughbreds with a washout (break) period of one week between treatment with saline (control), a nerve blocking agent, and electro-acupuncture. The horses were fitted with special shoes that had adjustable screws, which could be tightened to add pressure to the sole, thus inducing lameness. Their lameness was evaluated based on the standardized lameness grading score and by stride length.

Lameness score increased significantly in all groups when the screw was tightened. When horses received saline treatment, there was no significant change in lameness score. With treatment with the local anesthetic, the lameness score was reduced and returned to the baseline score (score before the screw was tightened). With treatment of electro-acupuncture for 45 minutes at a frequency of 80-120 Hz, the lameness score was reduced significantly, but did not return to normal. This indicates that the analgesic effect is not as nerve blocking as local anesthetic, but that acupuncture's effect is related to the nervous system. The results were similar for stride length, with local anesthetic returning the horse to normal and electro-acupuncture giving a significant reduction in lameness.

Researchers also measured the plasma concentration of beta-endorphins and found that acupuncture caused the release of beta-endorphins, while beta-endorphin levels continued to decrease with saline and nerve blocking once lameness was induced. Since there was no significant change in plasma adrenocorticotropin concentration after acupuncture stimulation, it is suggested that beta-endorphins might be released from somewhere other than the pituitary gland.

Thermography

A recent study determined that thermography is a useful tool for diagnosing problems in the racehorse before clinical signs appear. Being able to spot an injury early could allow trainers to adjust training schedules and veterinarians to treat an injury before time is lost from training by a more serious injury. Thermography measures heat emitted from an object. Since heat is a sign of inflammation, it has been quite effective in the evaluation of some inflammatory processes in the horse.

Tracy Turner, DVM, MS, presented the results of a two-year study at the AAEP Convention. During the first year, 225 thermal studies from 45 horses under seven different trainers at Canterbury Park in Shakopee, Minn., were examined and compared with notes from the trainer and veterinarian. It was found that thermography results agreed with trainer concerns 88% of the time and were consistent with veterinary findings 95% of the time. In each injured horse, the site of the injury was identified with thermography at least two weeks before the injury showed clinical signs.

During the second year, 461 thermographic evaluations were made on 50 horses from 10 different trainers. That year's results coincided with trainer's concerns 94.5% of the time and with veterinary results 95% of the time. Thermography predicted the problems an average of 2.3 weeks in advance of clinical signs during the second year of the study.

Turner noted that when using thermography to predict problems, the most important thing to measure is thermal patterns. When a change in the thermal pattern is noticed, there might be a cause for concern.

Treating Sore Backs

"It requires a number of diagnostics to make sure that we're working with back pain," said Reynolds Cowles, DVM, during the table topic on treating sore backs. While veterinarians discussed some of the current back treatments, most of the session was spent discussing the causes and symptoms of different types of back pain.

Daniel Marks, VMD, described the signs of equine back pain, which include bald spots under the saddle, asymmetry of the back muscles that is apparent visibly and by touch, and a painful response to back palpation. Nerve blocking, thermography, radiography, and scintigraphy are useful diagnostic techniques, although not all are practical for every case.

Back pain can stem not only from the spine, back muscles, and limbs--it can also be indicative of gastric ulcers or enteroliths (stones in the digestive tract). Additionally, the influence of the rider and tack is often underestimated.

Popular treatments discussed included steroids given systemically, non-steroidal anti-inflammatory drugs, acupuncture, and extracorporeal shockwave therapy. Marks was emphatic that the first treatment for back pain should be to figure out what's causing the pain, then eliminate or alter the source.

Team Roping Horse Lameness

Team roping's popularity has exploded in recent years, with a consequent increase in the value of competition roping horses, said Richard H. Galley, DVM, of Willow Park, Texas. These horses must break from the gate as fast or faster than a racehorse, catch a steer, and handle the forces of the steer hitting the end of the rope and the added weight of the rider and heavier saddle as they attempt to accomplish a five- to seven-second run (if it's a good one). With all this physical stress, these now more valuable horses demand and get better veterinary care than many horses in earlier years.

Most roping horses are at least 12 years old, said Galley, and seasoned national competitors are often over 20 years old. These older, proven horses often have a high tolerance for pain, competing with lesions that aren't usually tolerated in other disciplines.

One problem with treating roping horses, Galley adds, is that the high popularity of the sport draws many less-experienced horsemen who might not recognize early lameness signs, which often appear to be training problems. For example, a sore horse might not want to enter the roping box or might avoid the steer. Also, these horses often change hands many times, so a complete medical history of their problem(s) might not be available.

High-quality X rays are essential to early lesion diagnosis. One obstacle to diagnosis with local nerve or intra-articular blocking is that since these horses train with many repeated runs, they might not work soundly even after blocking because they are expecting the pain, even if not feeling it. Also, the saddle might not fit properly, which could contribute to apparent leg lameness.

Injuries common to roping horses include suspensory injury, especially in the right foreleg of heading horses, osteoarthritis, distal hock injury, P2 fracture, and soreness in the pelvis or sacroiliac region from the horse handling the steer at the end of the rope.

Cutting/Reining Horse Lameness

The average cutting or reining horse today is small (14.2 hands on average), according to Bradley Jackman, DVM, MS, Dipl. ACVS, of the Pioneer Equine Hospital in Oakdale, Calif. In addition, horses are often started quite young for the futurities, in which they'll compete as 3-year-olds.

Add in the small foot common to these small, agile horses, and you can have concussion problems, he said. Fatigue can also contribute to lameness because in order for the horses to perform calmly, they are often galloped quite a bit before performing to take the edge off.

Common injuries include suspensory ligament injury and desmitis, palmar heel pain/navicular syndrome, distal tarsitis, stifle lameness, and back soreness. Thorough lameness evaluation and good-quality X rays, nuclear scintigraphy, CT, and MRI imaging are valuable in diagnosing problems, Jackman said. Treatment might include oral pain medication, intra-articular injections, rest, controlled exercise, support bandaging, surgical ankylosis (joint fixation), and/or corrective shoeing.

While conformation can certainly contribute to problems, "I hate to absolutely link conformation and ability," he commented. "Some of the best athletes walk like ducks, while some are perfect, but can't work their way out of a paper bag."

He encouraged close attention to hoof care and shoeing, adding that a horse can rarely go more than six weeks between shoeings and still perform well. He also said that long toes, poor heel support, and delayed breakover are common problems.

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