For most clients their horse is viewed as or performs as an athlete. In many ways the needs of these horses are not much different than human athletes. As a comparison human athletes must focus on mental and physical health as well as fitness and training. For most competitive amateurs and certainly professional human athletes musculo-skeletal comfort is critical to their ability to perform. On the professional level detection of human orthopedic and musculo-skeletal issues is simple, the athlete tells the coach or the team doctor about an ache or pain and the detection process is over and the diagnosis is well on the way. At this point the doctor already has a localization of the pain and even a description as to the history behind the pain date or time of onset, any traumatic event, type of pain, level of pain and constant versus intermittent nature of the pain. But the detection and then diagnosis of musculo-skeletal abnormalities in our quadruped athletes is not quite this easy, we do not have the advantage of verbal communication and so the task becomes a much greater challenge for both the owner and the attending veterinarian. To further complicate the issue for many of our equine athletes, finances must limit the degree of diagnostic work up, as there are no insurance company or multimillion dollar contracts protecting the investment as in professional human sports.
Lameness in the horse is considered any disturbance or abnormality in the horses' natural gait. This disturbance or abnormality may be due to mechanical differences in the limbs, conformational defects or asymmetry in the body, or it may be caused by pain due to soft tissue, articular, hoof capsule, or neurological disturbances. A critical point to remember is that the majority of lameness' in horses go undetected. These are mild to moderate lameness' that the owner and rider are not aware of either because the issue is subtle enough that the horse is not "talking" about it or the horse is "talking" but there is nobody listening. When a horse does "talk" to us about their lameness it is either through the way they look as they are moving, the feel (to a rider) of the way they are going or through their actions or behaviors in not wanting to perform. For the average owner the more severe lameness' can be detected from the ground and the more subtle lameness' may be easier to detect as a rider. On the ground a lame horse will actually have a stride abnormality that may be detected audibly as well as visually, this deviation may be visible at the walk but many times will not be manifested until the horse is either trotted or cantered. Unless the horse has a significant lameness most owners do not have the training to visualize slight gait defects and so for the more subtle lameness the owner should be paying attention to some of the more common signals while riding. The common signals include an uneven stride, a cold back with excessive hollowing or dipping, evasion of the bit, swapping of leads, unwillingness to accept a particular lead or gait, acting out, unwillingness to perform or the progression of any of these "behavioral" problems. It should be obvious that as an owner there is little hope of diagnosing lameness in your horse if the detection phase is missing and this detection is oftentimes "written off" to behavioral problems.
So now, what to do if you do think that your horse may be lame? For some people the answer is simple, and they will immediately call for their veterinarian to evaluate the situation. But for most people a rule out of any obvious cause will come first and this will include checking for a pulled shoe, bruised foot, foreign object in the foot, traumatic injury or any observable heat or swelling of either a soft tissue structure or of a joint. This evaluation may be performed for various reasons. The owner may want to see if the cause of lameness is a problem that they are comfortable with treating on their own. Or the evaluation can be made to aid the soon to be attending doctor by providing additional information on the nature of the original injury or findings. Assuming that the problem is not easily detectable or treatable by the owner, a veterinary lameness evaluation and pursuit of a diagnosis will be required.
The first step for the attending veterinarian is to determine which limb or limbs are affected. Many lameness' involve multiple limbs and also multiple problems. For instance the primary lameness may be due to osteoarthritis in the hind limbs, but several secondary problems (especially if the condition is chronic or long standing) may exist. The secondary issues may be inflammation of the fetlock joints on the front limbs and tightness and cramping of the musculature of the lumbar spine. The veterinarian will proceed with a history of the complaint, observation of the horse at rest and then observation in motion. While at rest the veterinarian may complete any or all of the following procedures, palpation of the limbs, flexion of specific joints of the limb, palpation of musculature, palpation of the back and spine, hoof tester evaluation and possibly even rectal palpation. These procedures may come before or after watching the horse in motion depending upon the type of lameness suspected. At this point the veterinarian is still looking to isolate the lameness to either a limb or limbs and further more a specific area on those limbs. Should the veterinarian still have question as to the precise region that is causing discomfort they may proceed to performing a series of chemical nerve "blocks". The blocks are preformed to eliminate sensitivity from a region. Once the area is blocked a second evaluation of the lameness will determine if the blocked region was the source of pain. If the lameness was significantly reduced or eliminated the region blocked is concluded to be a source of pain. The veterinarian in many cases will still not have a diagnosis although there may be the discovery of multiple sites of pain. Additional secondary diagnostic procedures will be needed to help in determining the precise diagnosis.
Secondary diagnostic procedures may include radiographs, ultrasound imaging, video recording, joint fluid analysis, nuclear scintigraphy, magnetic resonance imaging (MRI), or exploratory arthroscopy. As one can see the extent of work that may have to be performed to diagnose and lend a prognosis and treatment plan for a particular lameness and or lameness' can be quite extensive. It is reasonable then to expect that the more experienced and more intuitive your veterinarian is at determining both the source of pain and the probable diagnosis the faster and easier (and of course less expensive) it will be to move on to a treatment plan.
Although the above procedures sound quite complicated detailed and exhausting and they can be, many of the lameness' can be diagnosed without all of the steps listed above. Many of the secondary diagnostic procedures other than radiographs and ultrasound imaging are rarely employed, due to the difficulty of the procedure in large animals, the limited availability of the procedure and the cost of the procedure. As with most health issues early detection, proper diagnosis and effective therapeutic intervention can minimize the disease process and maximize the athletic career of the patient.