AAEP Ask the Vet: Lameness Injuries and Diagnosis

  1. Lameness Injuries and Diagnosis
    1.  Can rotation in the feet be corrected? My vet says, no, but that the coffin bone can LOOK better and the horse can be made more comfortable by proper trimming. However, once rotated, always rotated. Is she correct? 

      Your vet is correct, but it is worth explaining more about the condition of laminitis that leads to rotation of the coffin bone inside the hoof capsule to fully understand why she is correct. The coffin bone is attached to the hoof wall by microscopic structures called "lamellae." The lamellae are sort of like strips of velcro -- one side of the velcro is attached to the hoof wall, and the other side is attached to the coffin bone. Unlike velcro, however, the attachments are permanent. Once one strip is ripped off the other strip, it cannot be reattached. The hoof capsule of the horse is constantly growing and regenerating, but the lamellar attachments do not regenerate to any appreciable degree. This is why permanent damage to the lamellae cannot "grow out" over time.

      Laminitis, or founder, refers only to inflammation ("itis) of the lamellae. The degree of inflammation will vary with each individual case. If the inflammation of the lamellae becomes severe enough, the lamellae will become damaged and start to weaken. Initially, this causes the lamellae to stretch but not break. If the lamellae stretch far enough they become structurally weakened and can no longer support the weight of the horse or oppose the pull of the deep digital flexor tendon at the bottom of the coffin bone. The lamellae will then give out leading to sinking in the first case, or rotation in the second case.

      It can be difficult in some cases of laminitis to determine whether or not permanent structural damage to the lamellae has occurred. The only way to tell for certain in borderline cases is to look at the lamellae under a microscope -- but we do not do this in living horses because taking that kind of a sample causes too much damage to their feet. Instead we rely on post-mortem study of horses who have been euthanized due to laminitis to study these changes. For the practitioner in the field, we can only infer what the status of the lamellae are by closely monitoring parameters we can measure -- the horse's comfort level, venograms, and changes in the xray over time. Unfortunately, changes on an xray happen several weeks after they happen inside the hoof capsule so we are usually playing "catch up" with our trimming and shoeing recommendations. 

      Certain conditions in the foot may also mimic rotation and make the degree of laminitis look worse. A long toe that has begun to flare will give the appearance of rotation (as well as add mechanical stress to the lamellae), but can be corrected with proper trimming. Additionally, severe white line disease can cause separation of the hoof wall from the backside of the hoof "velcro" strip. White line disease can be difficult to treat in severe cases, but it can be improved, and treatment will improve the radiographic appearance of the foot.

      Good luck with your horse, laminitis is a difficult and frustrating disease for all of us. Heather Beach, DVM, Ashford, CT

      1.  I have a gelding that was diagnosed with navicular before he was 3-years-old. The veterinarian said he was probably born with it. I had such high hopes for his horse. The vet said I would probably have to put him down in a couple of years. I have tried shoes and barefoot. Could I send you his X-rays and you tell me what you think? Does any of those supplements help? I can't stand the thought of this situation. Any suggestions would be greatly appreciated. Let me know if I can send the X-rays please. 

        I am able to answer general questions, but not really able to help you with the specifics of your case in this format. I will give you some general information about navicular disease and other thoughts about young horses with serious problems however.

        The first thing you should know is that most horses with navicular syndrome do not have severe lameness. Navicular syndrome is more commonly a performance limiting disease and many horses with this disease can do just fine with light work if they are maintained with shoeing and other medications as needed. It is very common for navicular disease to be present in young horses, especially Quarter Horses, but having significant changes in a horse as young as yours may be an indicator that this is a more severe form of the disease. The navicular bone is a small bone in the heel of the horse. It's job is to act like a pulley, allowing the deep digital flexor to run smoothly around the heel as it attaches to the bottom of the coffin bone inside the hoof of the horse. Disease in this bone is usually caused by changes in the quality of the bone itself -- the bone becomes hard and brittle and can be more easily bruised from concussive trauma associated with riding, especially on harder surfaces. In more advanced cases, the bone can become very thin, and they can develop cystic lesions inside the bone. These lesions tend to be painful because they cause further inflammation and degradation of the bone.

        Therapeutic shoes can help maintain soundness in many of these horses for a very long time. As for supplements, I might consider putting the horse on MSM, but I would not expect this to drastically alter the course of the disease for your horse. Isoxsuprine is a medication often prescribed for horses with navicular disease. It alters blood flow to the bone by dilating the vessels slightly, to allow increased blood flow to the bone. This will help the lameness in some horses, while others do not show any improvement. I never expect isoxuprine (or any treatment) to improve the appearance of the bone on the xray -- I only look for improvement in soundness. I urge people who try isoxuprine to try it for at least 2-3 months to determine if it is helpful to their horse. Anti-inflammatory medications like bute can also be used to keep these horses sound and comfortable, but should be used at the lowest effective dose to minimize side effects. Once a horse is sound enough to do light work with shoeing and medication, I will often use joint injections (either coffin joint or navicular bursa) to help prolong soundness and quiet down inflammation. I really like to find a shoeing prescription and riding schedule that gets the horse as sound as possible first though, because these are the elements that will ultimately be responsible for the long term success of the treatment. It often takes multiple tries with different shoe/pad combinations before you find the one that really works for your horse so I always urge owners to be patient and keep trying. There is an intravenous medication called Tildren that has been used in cases of navicular disease with some success as well. Tildren works by slowing down active bone turnover. It will not work in all cases of navicular disease, and one treatment will not last forever, but it can be a very good option for maintaining soundness in some cases, although do be aware that it is an expensive medication, so it doesn't make sense for every one to try it. Finally, the last option for navicular disease is to have a surgical procedure performed that cuts the nerves to the foot so that your horse does not feel the pain anymore. There are some complications with this procedure, however, and in most cases it will only last for 3-4 years before the nerves start to regenerate and the horse regains sensation and becomes unsound again. 

        The most important thing that you can do for your horse is to have realistic expectations for him. Work with your vet to establish reasonable short term expectations, and find a good farrier who is willing to work with you and your veterinarian. We cannot "cure" navicular disease, we can only manage it. Good shoeing, medication, and a realistic and appropriate work schedule can keep many of these horses sound any happy for some time. Euthanasia would be considered if the horse's quality of life was suffering -- a chronic lameness apparent at the walk that did not respond to shoeing changes or bute, for instance. Heather Beach, DVM, Ashford, CT

        1.  I have an 18-year-old mare that is lame in her back, right leg. The first veterinarian performed four (4) chiropractic treatments to no avail. The second veterinarian determined she was “flexior positive” with the possibility of being bilateral lame and in the hocks. Radiographs helped to determine this diagnosis. What could have caused this and what are her options for treatment? 

          It is quite common for horses of any age, but particularly older horses, to have a bilateral (meaning both hind legs are affected) lameness that is associated with their hocks. It is also quite common for them to present like your horse does with only one leg appearing to be lame at first glance. This is due to degenerative joint disease of the joints of the hock, resulting in arthritis. The hock joints are a very common site for arthritis in horses, but the good news is that there are many treatment options available and most horses respond very well to treatment of these joints.

          Arthritis in the horse results from a variety of factors. It typically starts with some inflammation in the joint, either because of trauma, repetitive stress from high intensity exercise, conformational defects that put abnormal stresses on the joint, or as part of the normal aging process that we all go through. As time goes on, the inflammation will cause the joint fluid to become thin and provide less cushion and nutrients to the cartilage within the joint. As this process continues, it stimulates bony growth at the edges of the joint that initially appear as "bone spurs." The degree of arthritis present in the joint will depend on the amount of inflammation and the degree of cartilage erosion present. It is important to know, however, that horses may be sore and have positive flexion tests even when they are at the early stages when very little arthritis is present. Conversely, many horses that are at the end stage of hock arthritis are quite sound, because the joint is stabilized and the bone is no longer actively turning over anymore.

          Treatment options will vary and will depend on your budget, the degree of lameness and severity of arthritic changes in the horse, whether or not there are other sources of lameness in the horse, as well as the athletic demands of the horse. A pleasure horse that goes on light easy trail rides on the weekends may do well with just a little bit of phenylbutazone (bute) given before and after a ride in order for her to stay comfortable and be able to do her job pain-free. A more athletic horse may need more targeted therapies. Some horses will respond favorably to a systemically administered joint product such as Legend or Adequan. These are good first options for horses that do mild to moderate exercise, and have mild to moderate lameness issues, or for horses that have lameness issues in multiple joints. Legend is a product that your veterinarian gives intravenously, and is made from hyaluronic acid, which is a component of joint fluid. Adequan is given intramuscularly and is made of a chondroitin sulfate precursor, called polysulfated glycosaminoglycans (abbreviated PSGAGs). Both products are thought to work by down regulating inflammatory mediators in the joint, but there is only limited data available about exactly how these products work. The final option to treat hock pain is with injections of medications directly into the joints of the hock. This is a more direct way of treating the pain and inflammation within those joints. Typically this treatment is done with a corticosteroid and a synthetic hyaluronic acid. Hock injections are very effective at treating pain in the hocks and the effects typically last for 6 months to a year for most horses, although some horses may show symptoms again sooner, and others will not need to be retreated again after the cycle of inflammation is stopped once.

          There are a few more options for treatment of very advanced cases of hock arthritis -- it would probably be best to get a consultation with a veterinary surgeon before considering more advanced options, and in most cases I would only consider those treatments if the horse failed to respond to standard hock injections first. You should discuss all these options with your veterinarian before you decide which treatment option to pursue. Most horses with arthritis will also benefit from regular, low intensity exercise to help keep them moving and fit as well. Heather Beach, DVM, Ashford, CT

    2.  I have an older gelding that has arthritis in his stifle joints. Other than Glucosamine andChondroitin sulfate, what else can I do to keep him comfortable? 

      Oral joint supplements can be helpful for arthritis cases, but often times they need a little something else to really help control the pain and inflammation. Giving the lowest effective dose of bute is a great way to make an older horse feel better while minimizing side effects. I usually prescribe a twice a day regiment for a few days, then back down to once a day, then every other day. I ask the owners to notice how the horse responds and to see if they still see a positive response at the lower doses. Often times, the horse will end up on one gram of bute per day, and do very well on that for a long time. In cases where there is a strong concern for side effects due to bute, Equioxx can be substituted instead. 

      Beyond just giving an anti-inflammatory medication like bute, I will also use some of the injectable products like Legend or Adequan in older horses with significant arthritis. Each of these products requires a three week loading dose phase, then a maintenance dose. Not every horse responds the same to these products, but if they are going to have a favorable response, it usually happens during the loading dose phase, which makes it easy to determine whether or not to continue with the maintenance dose.

      Finally, arthritis tends to respond well to low level exercise. If your horse is retired, consider going on some walks with him. A nice leisurely 15 to 20 minute hand walk per day could be good for both of you, and gives you some extra time to spend with your older horse. If you can, try to make sure your horse has access to plenty of turnout and avoid big steps in or out of his stall so he doesn't have to really pick his legs up to get in and out. Heather Beach, DVM, Ashford, CT