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| THE VET'S NOTEBOOK |
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Guidelines for Detecting Lameness, Part II
by Dr. David Ramey, DVM |
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In my previous article, I offered some general guidelines on how to recognize when a horse is lame. This month I will explain how a veterinarian determines which leg is affected and some methods used to determine what is causing the problem.
After a thorough physical examination and watching the horse in motion, a veterinarian will usually have a good idea in which leg the horse is lame. Once the focus is directed at one leg, a number of things can be done to locate the source of the problem.
Any areas of heat, pain or swelling are examined thoroughly. Sometimes it is possible to determine immediately that a particular area is causing the lameness. For example, swelling in a tendon that is accompanied by lameness, heat, and pain when touched is a pretty good indication that the tendon is the source of the problem. Not all lameness is easy to determine, however, and in more difficult cases, a systematic method of determining the location of the lameness is required.
Hoof Testers -- If there are no obvious areas that are sore to the touch, the foot is usually examined first. One commonly used device is a hoof tester. This device applies pressure to the foot when it is squeezed and if a horse is sore, he will react by attempting to withdraw his foot from the testers. If a spot on the foot is suspected of being sore, the horse can be trotted after pressure is applied to that sore area. If the horse's lameness at the trot is worse after hoof tester pressure has been released, then it is likely that the source of the problem has been found.
Flexion Test -- Another useful way to diagnose lameness is to apply pressure, or stress, a suspected sore spot on the limb. For instance, if a horse has a sore knee, holding the knee in firm flexion for a minute before trotting him may cause the horse to be sore for a few steps. This situation is similar to what would happen to you if you had a bad knee and were asked to crouch for a minute before running off. You'd be limping for a few steps, too. This principle can be applied to a variety of lamenesses, but interpretation of the response is something of an art. Unfortunately, some normal horses will be sore after stress tests, so the test must be interpreted in light of all of the clinical signs that the veterinarian finds.
Nerve Blocks -- Nerve blocks are another way to discover the location of lameness. The nerves in the horse's limbs lie close to the surface and, by putting a small amount of anesthetic over the nerve, the areas supplied by that nerve will go numb. Local anesthetics can also be put into joints and can block the pain caused by joint-related problems. Using local anesthetic blocks is a process of elimination. If a horse is sore in a particular area and that area is made numb, the horse will appear to be sound when trotted because the spot no longer hurts. Thus, by using nerve blocks a sore spot in a leg can be isolated. Generally, nerve blocking starts from the ground and works up. This procedures can be time consuming, but it's often the only way that the location of a lameness can be determined.
After discovering where the horse is lame, further diagnostic tests to determine the extent of the problem may be required. Depending on the injury, the most common choices would be either radiographs (X-rays) or ultrasound.
X-rays -- X-rays are a form of radiation generated by a portable X-ray tube. The X-ray camera is placed on one side of the limb and a plate, containing X-ray film, is placed on the other side. The density of the tissue between the camera and the film determines the amount of X-rays that reach the film. Bone stops a lot of X-rays and it looks white on the film. Air and water (soft, non-bone tissue is mostly water) allow most of the X-rays to reach the film and they appear black on the film. Therefore, X-rays are useful primarily for disorders of the bones. X-rays of lame horses can be compared with those of normal bones and recommendations for treatment can be made based on the findings.
Ultrasound -- Ultrasound is the best method available for examining the soft tissues of the leg because it is not possible to accurately evaluate a soft tissue injury to the tendons or suspensory ligament without this technology. For example, even though a swollen tendon might be an obvious problem, the only way to determine the extent of the injury is to examine it with ultrasound. One noted expert in the field has estimated that ultrasound demonstrated that his clinical impression of injury was wrong 25% of the time! With ultrasound, what appears on the surface to be a minor injury may be determined to be quite significant. Conversely, what may appear to be a major problem can sometimes be no big deal. Based on the severity of the injury, a course of treatment will then be prescribed.
© 1998 by Dr. David W. Ramey. All Rights Reserved.
Dr. David Ramey is a 1983 graduate of Colorado State University. He is the author of numerous books and articles on horse health, including Horsefeathers: Facts vs. Myths About Your Horse's Health and the Concise Guide series on equine health care. He can be reached at (818) 953-8528. |
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