Equine Lameness
Our practice frequently gets called to examine a horse for a lameness problem. Horses are exposed to numerous perils in athletic events and activities that can cause injury resulting in lameness. For purposes of this discussion we will define lameness as any alteration in the horse’s normal gait. Gait alteration is usually due to pain but in some cases alteration of gait can be the result of fibrous scar tissue or calcified adhesions restricting normal movement. This latter situation is called a mechanical lameness. Lameness can result from pain almost anywhere in the body, but most commonly the muscles, bones, and joints of the horse and other associated soft tissues that support the joints are involved. Infected areas, inflamed lymph nodes, and even pain from a mare’s heat cycle can cause alteration of gait. Sometimes swelling and pain is evident. Many times, however, the site of soreness is not so clear and a careful examination routine must be followed to search for the lameness. These are the times when we wish that the horse could talk to us.

The first part of the lameness exam is done with the horse at rest. A medical history is taken, paying special attention to any past musculo-skeletal problems and the past and present work schedule of the horse. Observations of the horse by the owner or trainer are critical at this point to best understand when the problem began and how it developed. Did lameness occur suddenly or has there been a slow progression to the current state? You know your horse best and we need your input. It is also important to understand what the future plans are for the horse. Is it a performance athlete or an occasional recreational riding companion?

A visual assessment of the horse’s physical condition and conformation are important. Crooked legs, small feet, or asymmetrical muscle development can be clues to the problem areas. Hoof or shoe wear can be an indication of abnormal foot flight and landing. Is the hoof trimming and shoeing correct? Do the pastern and hoof wall angles match? Are there any old wounds or scars? Does the horse rest one leg consistently or constantly shift weight from one leg to the other? The head and neck including the teeth are evaluated. Are there bit problems?

The neck, back, and gluteals areas should be palpated for points of pain or lack of symmetry. Any abnormal areas will be re-evaluated after warm up exercises. Lateral and dorsal-ventral flexibility of the entire spine is checked.

The next evaluation is with the horse in motion. The horse is observed at the walk and trot, on soft and firm ground, and in a straight line and circling. Especially with hind limb lameness, observation at the canter is also very useful. Most of the work is done on a lead line or longe line, but occasionally seeing the horse work under saddle is helpful. During the in-motion phase, the veterinarian is looking for shortening of the stride, irregular foot placement, head bobbing, stiffness, abnormal hoof flight pattern, reluctance to accept a particular gait or direction of movement, and any other deviations from normal.

Palpation of the flexor tendons and the suspensory ligament along the back of the cannon bones is done in a flexed, relaxed position.

Hoof testers are used to apply pressure to the soles of the feet to detect undue sensitivity or pain. Each area from heel to toe and then the frog are check carefully. The heels are compressed and the hoof wall may be percussed. Abnormal reaction in any area can mean bruising, abscesses, or other internal hoof problems.

Hoof Testers
At this point, joint flexion tests are done. Each leg is examined in turn by holding the lower and then the upper joints off the ground flexed for 60-90 seconds and then released as the horse is asked to trot off. Any alteration in gait with these tests can point to an area of potential problem. The flexion puts extra stress on the joint structures, tendons, and ligaments, and can suggest an area of soreness not seen in normal movement.

Having done all of the above, the source of lameness should be narrowed down to the offending leg or legs. Now a specific diagnosis is needed before rational treatment can be attempted. Often the next step is to perform diagnostic nerve or joint blocks. Small amounts of local anesthetic are injected over specific nerves or into specific joints to temporarily desensitize that particular region or specific joint. This desensitization lasts about one hour. Because the source of about 80% of all foreleg lameness is from the fetlock down, the blocking is generally done beginning from the lowest parts of the limb and working upwards. In the hind limb, this pattern may change because of a higher prevalence in other areas. For example, hock arthritis is very common in all performance horses. One area at a time is deadened until the lameness disappears. Once this occurs we know where the pain is localized. The next job is to find out why the pain is there.

Radiographs (x-rays) are used to examine and evaluate damage or changes in bones such as malformations, fractures, bone chips or bone spurs. Osteoarthritis (bone spurs in the joint) is a frequent finding in performance horses.

Ultrasound (sonography) is used to evaluate soft tissue support structures such as tendons and ligaments. Muscle calcification and tearing can also be evaluated. This is especially useful to determine the degree of initial damage and follow repair throughout rehabilitation. In this way the horse can be returned to work at a demonstrably correct time as the tissues heal.

At referral hospitals more advanced diagnostics such as nuclear scans, CT and MRI are becoming more available.

Once the source of lameness is discovered, treatment is planned. Often several types of therapy are used together which could include rest, cold applications, change of exercise level, changes in shoeing, pain relief medication, anti-inflammatory medications, support wraps, or regional or intra-articular (joint) injections. Emerging therapeutic use of stem cells and platelet rich plasma and shock wave therapy are showing promise at specific sights, as well. Additionally, IRAP, a process of harvesting the horse’s own blood to collect anti-inflammatory proteins and injecting the refined produce into a joint has shown good results. In some cases an injury or condition may demand a temporary or permanent change in job description for the horse.

The most widely used pain relief drug is Phenylbutazone (bute). This remains a very useful drug because it also reduces inflammation in swollen tissues so it can aid healing as it relieves pain. Flunixin (Banamine) acts in a similar way. Firocoxib (Equioxx) is a third NSAID used for pain and inflammatory control and may be less likely to cause gut reactions. All of these can be given orally, and bute or Banamine also by injection, and are helpful in many musculo-skeletal injuries.

Corticosteroids (cortisones) are potent anti-inflammatory drugs that are commonly used with very good results, but like bute and Banamine, must be carefully controlled because of problems that can result from over usage. Specific cortisones are actually protective to joint cartilage. Properly used at correct doses bute, Banamine, and selected cortisone drugs are safe and very beneficial. Rest or reduction of exercise is generally also indicated when these medications are given.

When a joint is damaged through trauma or chronic irritation of bone spurs (osteoarthritis), injury to the tissue cells that line the joint capsule causes release of several enzymes that are irritating and cause further damage, pain, and deterioration of the joint fluid and cartilage. This results in decreased lubrication of the joint and the cycle of inflammation, pain, and damage continues. The most effective way to reverse this inflammation and pain is to inject triamcinolone into the damaged joint. This specific, potent cortisone drug has a healing effect on damaged cartilage and usually shows positive results in an arthritic joint within 10-14 days. Hyaluronic Acid, HA, may be used with triamcinolone to directly improve the quality of joint fluid in an inflamed or arthritic joint.

There are some oral Nutriceutical supplements that can also be beneficial but this is an unregulated field and many products on the market are ineffectual or untested. New clinical trials show that the minimum effective concentration of glucosamine chloride is 10 grams (10,000 mg) daily and that unsaponified soy and avocado (ASU) extract reduces joint inflammation although they have no effect on pain. Cosequin ASU is chondroitin sulfate, glucosamine and avocado/soy unsaponified in a granular form.

The main therapy for tendon and ligament repair is rest and slow return to activity. Stem cells harvested from the horse and injected into the damaged areas can improve the quality of healing and this treatment is advisable for severe tendon or ligament injuries. New therapies include plasma rich platelets and shock wave therapy.

Damaged muscles respond mainly to rest and anti-inflammatory medications. We may prescribe Surpass, a topical anti-inflammatory medication, to massage over inflamed muscles to reduce discomfort and swelling.

Every horse is different. Each lameness condition is different and each owner has different expectations of performance. As horse owners ourselves we understand the important part your horse plays in your life. We feel that the best way to serve you and your horse is to perform a thorough exam, use appropriate diagnostic methods and offer you the best treatment we can, based on a specific diagnosis. In this way, with your help, we can get you back in the saddle as soon as possible.
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