Lameness is described as “an incapability of normal locomotion, deviation from the normal gait”
Thus even subtle changes, such as “scratchy” horses should be considered to be lame and require further investigation. Lameness is THE most common reason for poor performance in equine athletes, especially in racing thoroughbreds. Most lameness cases can be diagnosed and treated successfully if the horse is examined early in the lameness process. Waiting until a horse is overtly lame (ie easily seen at a walk) before veterinary assistance is sought often means that the injury has progressed to stage where irreversible damage has occurred.
Lameness investigation is a vital tool in finding and managing the cause of an abnormal gait. Lameness can be pain induced or mechanical in nature.
In the majority of cases the process involves observing the horse at a handheld walk, trot or lunge. In rare cases lameness can only be detected in ridden work.
Lameness investigation begins with answering the following questions:
- Is the horse lame?
- Which limb or limbs is the horse showing a changed gait in?
- Which part of the limb is affected?
Experience and an understanding of equine biomechanics as well as a thorough knowledge of anatomy are required to answer these questions correctly. Often the source of the lameness is relatively obvious and easy to locate, however many lame horses are quite difficult to diagnose and require a more thorough examination. A series of specific diagnostic tests, starting in the foot and working upwards is required for a thorough lameness examination.
Hoof testers can be used to test whether there is pain in the foot or not and are an invaluable tool in the location of stone bruises, hoof abscesses, navicular bone problems and many other sources of foot pain. Flexion of the individual joints within a certain limb can exacerbate the lameness and help to locate the area of pain. Flexion tests usually involve holding the joint or leg in a flexed position for a certain time and then observing the trotting horse to asses any change to the lameness. Once a particular area of the limb is suspected a series of diagnostic nerve blocks and/or joint blocks can be used to confirm our suspicions or to rule out other possible causes. A nerve block involves injecting a local anaesthetic, over the nerves, at specific points in the limb to temporarily remove the source of the pain. A specific sequence of nerve blocks is used, again starting at the lowest point working up the limb. If a particular nerve block is positive and alleviates a lameness it allows us to concentrate on that particular area of that limb with further diagnostic procedures such as radiography(X-rays) or ultrasound scanning.
To get to this point sounds simple but it can be a tedious exercise and enough time should be allocated for a complete investigation ranging from 1 hour to a full morning/afternoons work. Each nerve block can take up to 20 minutes for a full effect. It is also important that a firm level surface is available to trot the horse up in a safe quiet environment away from distractions of other animals, people and traffic. Ideally lunging facilities should be available if required to ensure a proper investigation.
Only once a proper diagnosis has been made can a suitable management protocol be implemented to speed the horse’s recovery to its normal use.