VL 11a Scan/Click to view video. www.getsound.com/tutorials/11a
Appropriately, many practitioners will presume that axial asymmetry is either artificial (referred) or compensatory if it coexists with peripheral lameness. In these instances, the median anatomy will assuredly display unnatural movement to adjust for gait deficits in one or more limbs, thereby making it extremely challenging for the observer to validate the primary contribution of any axial component.
Interestingly, horses with authentic axial lameness are more likely to avoid movement altogether as opposed to moving irregularly. As previously discussed (in chapter 5—p. 26), the relative proximity between contralateral axial structures in combination with the horse’s emphatic desire to safeguard painful areas can make effective assessment of the median anatomy (by itself) very perplexing.
For these reasons, it is important that we do everything at our disposal to simplify the process: observing the horse on a regular basis (from one day to the next), asking the horse to move in concentrically smaller circles and appraising the effect of a rider’s weight are all common techniques intended to clarify our visual assessment of head, neck, and back motion.
The Head and Neck
The horse’s head and neck are quite heavy, accounting for almost 10% of the entire body weight. The head is located a considerable distance from the trunk on account of the appreciable length of the neck. As such, it serves as an extremely effective means for transferring weight, particularly that associated with the front end. It is also a very large and visibly prominent structure that can be easily tracked with our eye. Based on these characteristics, the horse’s head can essentially be considered a peripheral structure that aptly awards the observer with an explicit marker for assessing lameness. In combination with the withers, the head and neck are evaluated foremost during visual lameness assessment (see chapter 23 and VL 11b).
VL 11b Scan/Click to view video. www.getsound.com/tutorials/11b
Notwithstanding, the horse’s head also embodies the aspect of anatomy most often utilized to emit emotion, such as anxiety or resistance. Abnormal movement related to these forms of expression can be very difficult to interpret, and should, therefore, be considered in conjunction with how the rest of the horse’s body is moving.
12 Consistent versus Intermittent Lameness
Most forms of lameness are apparent from one day to the next. Consistent lameness usually commands our attention until we accurately identify its cause. Inconsistent or intermittent lameness, on the other hand, is less captivating because we’re not always convinced that there’s actually a performance problem with the horse.
All cases of intermittent lameness entail some form of instigation or prompting. In other words, there is something that triggers the observed gait abnormality(ies). It could be extrinsic (such as a rock lodged in the foot, cold weather, very deep footing, a large bandage) or it could be intrinsic, resulting from pathology within the animal itself. The key to accurately decoding inconsistent lameness lies in our ability to identify its trigger(s).
As attentive equestrians, it is our duty to make sure that we don’t overlook any intrinsic excuses for intermittent lameness.
Tripping
Most horses have tripped at one time or another. Some might stumble on a regular basis while others falter sporadically. Most riders implicate extrinsic causes, such as holes in the ground, dramatic inclines, or deep footing (VL 12a). Others believe that their horses are inherently “lazy” and unwilling to pick their feet up enough to clear the terrain. Albeit there are many extraneous causes for tripping, we should always consider the possibility that the horse is faltering as a result of an unsoundness, especially if it occurs with some regularity and/or if certain limbs are exclusively affected. Indeed, there are multiple forms of lameness that feature tripping as a symptom (fig. 12.1). It is important to remember that the inciter may be ever present, even though the horse only trips on occasion.
VL 12a Scan/Click to view video. www.getsound.com/tutorials/12a
12.1 Intrinsic Causes of Tripping in the Horse
| Instigator: Premature breakover of the limb—the horse picks the limb up before the amount of leverage required to break over naturally is realized. | |
| Possible Underlying Circumstance(s) | Comments |
| Excessive toe length of the foot. | The horse’s toe(s) may be so long that he/she is unable to acquire enough mechanical leverage to break the foot over naturally. In this scenario, the horse simply “runs out of leg” and has to pick the foot up before the natural breakover process can be initiated. A person can relate to this dilemma by attempting to walk or run while wearing swim fins on his/her feet. The amount of leverage afforded by the fins is too much for the length of the human leg to accommodate. Hence the person is forced to pick his/her feet up prematurely, thereby increasing the risk for tripping. |
| Excessive tension of the deep digital flexor tendon (DDFT). | The process of foot breakover is initiated by tension along the deep digital flexor muscle and the distal accessory ligament (DAL or inferior “check” ligament), both of which act through the deep digital flexor tendon (DDFT) and suspensory ligaments of the navicular bone (chapter 20, p. 136). Excessive tension and/or pain associated with one or both of these structures can prompt the horse to pick the foot up prematurely, thereby increasing the risk for tripping. |
| Excessive tension of the distal accessory (or check) ligament (DAL). | |
| Pain associated with the deep digital flexor tendon (DDFT). | |
| Pain associated with the distal accessory (or check) ligament (DAL). | |
| Pain associated with structures that the DDFT influences, such as the navicular and coffin bones. | The events that precipitate breakover ultimately involve anatomic structures that reside within the foot. The horse might choose to pick up the foot prematurely in an attempt to avoid pain if it’s generated when increased tension and/or pressure is applied to one or more of these structures. |
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Instigator: Decreased proprioception—a lack awareness pertaining to the spatial orientation
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