Sometimes it’s obvious, sometimes it’s not, but early detection is always critical.
Article reprinted courtesy of the UC Davis Center for Equine Health
Veterinarians will use several techniques to determine lameness in a horse. Some types of lameness are obvious. The horse that is pointing a hoof and barely loading the limb (or displaying a large head lift when the affected limb is loaded) needs help.
Subtle lamenesses, however, are more difficult to recognize, and early detection and intervention are often key to successful resolution.
Lameness is a symptom that something within the limb or body hurts enough that the horse alters its gait to control the amount of load the affected limb has to bear. This alteration in load usually creates an asymmetry to the gait.
Front limb lamenesses are more common, because the horse carries 60 percent of its body weight on the forelimbs. Horses use their heavy head and neck to control the amount of weight delivered to each front limb. Head motion and position can be helpful when evaluating front limb lameness with the old adage, “down on sound.”
Hind limb lamenesses can be more difficult to detect, and movement of the pelvis will help to indicate asymmetrical load behind.
There are three phases to loading of the equine limb, and certain types of lamenesses will be most obvious during one of these phases:
The amount of force at impact with the surface is dependent upon the horse’s speed and weight, as well as the firmness of the surface. As the hoof meets the surface, it must slow down and engage the surface in order to push off. This natural deceleration of the foot must combat the forward motion of the horse.
If the deceleration is too rapid, as can occur with certain types of footing, then the musculoskeletal system of the horse is more likely to be strained. Most front end lamenesses are impact lamenesses, and the horse will use its head to control the load. When the impact lameness is behind, the horse will often display an asymmetry in pelvic lift. An ideal surface will cushion impact, allow for grip, and then transfer some energy back to the horse.
This occurs when the horse’s hoof grabs the ground surface and propels against it, creating forward motion. Push off engages different muscles and support structures than impact, and many hind limb lamenesses are associated with push off. These horses will often drop their pelvis due to lack of impulsion.
The swing phase of the stride occurs while the horse’s limb is in flight, after push off and before impact. There is no load on the leg during this phase, however, muscles, tendons and ligaments are necessary to create the flexion and extension that are necessary to create the swing. Swing phase lamenesses are less common, but do occur.
Sometimes the gait asymmetry is only present with the rider on board, or performing a certain task; this makes evaluation under tack an important part of a lameness exam. Riders can help veterinarians by sharing nuances noticed while riding.
Subtle lameness can manifest as a simple aversion or difficulty in performing a certain movement, or traveling in a certain direction. Examples of this can be reluctance to canter or lope, failure to hold lead or preference for striking off on one limb, ear pinning, tail swishing or kicking out in certain movements. Jumping horses may consistently add a stride or jump to the side of a fence.
Saddle slip has recently been associated with hind limb lameness, with the saddle often slipping to the lame side. In the majority of cases, lameness is most obvious in the trot or jog. If a gait asymmetry is detected, but the involved limb is not obvious, it is most likely the limb on which the horse spends the least amount of time.
The “Law of Sides” suggests that if diagonal shortness is apparent, the primary problem is most likely coming from the front end. If there is trouble determining front or hind on the same side, the problem is most likely coming from the hind end. Involving a veterinarian with experience in lameness detection early on is wise and can prevent more serious injury from occurring with continued use.
The key to successful resolution of lameness is an accurate diagnosis of why the horse is limping. Veterinarians are trained to palpate the anatomical structures of the horse and to evaluate joint range of motion and soft tissue sensitivity. They will observe the horse in hand and under saddle and note the most obvious lameness, followed by suspected compensatory lameness and secondary lameness.
Flexion tests can help to localize lameness and are often part of a routine lameness examination. Flexion tests are less accurate localizing a hind end lameness. It is difficult to isolate the hock from the stifle from the hip, as they are connected by the stay apparatus and flex together. Certain manipulations can increase the specificity of these tests.
Hoof testers are used to assess sensitivity of the foot. Eighty percent of forelimb lameness is caused by foot pain.
Nerve blocks involve the administration of a local anesthetic to peripheral nerves and/or joints to systematically desensitize areas and look for improvement in gait. Because a horse cannot tell us where the pain is coming from, we rely on nerve blocks to identify the area to be imaged. Certain areas of the body are difficult to block due to access or safety.
Some practitioners will augment the traditional lameness exam with other tools such as a chiropractic exam, an acupuncture scan, and/or the use of inertial sensing devices such as the Lameness Locator. Recent research demonstrated that 80 percent of horses with an abnormal acupuncture scan were lame.
• Horse owners should palpate their horse’s limbs and joints daily, and get to know the feel of their horse. Subtle temperature changes or swelling should be monitored and discussed with a veterinarian.
This article was published by the Center for Equine Health with funds provided by the State of Ca Satellite wagering fund and contributions by private donors. The CEH advances the health ,welfare, performance and veterinary care of horses through research, education and outreach.
Written by Article reprinted courtesy of the UC Davis Center for Equine Health.
Tuesday, 28 February 2017 02:06