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FAQ: Can the Q be used on a gaited horse?

By Kevin Keegan Kevin G. Keegan, DVM, MS, DACVS | Updated on | Data Collection, Data Interpretation, FAQ, Gaited Horses, KG Keegan


FAQ: Can the Q be used on a gaited horse?

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In general, the ambling (single foot, or 4-beat) gaits decrease the vertical movement of the horse's trunk, making it easier to “sit”. Consequently, to maintain some vertical momentum, the horse’s vertical head movement becomes exaggerated.  Because of the way The Q (Lameness Locator®) displays results relative to “expected” vertical movement, this may cause underestimated forelimb lameness, overestimated hind limb lameness, and increased variability.  Also, for the ipsilateral gaits, the evaluator must flip the hind limb results (i.e. reported RH lameness is really LH lameness), because the inference of footfall from the right forelimb gyroscope is off by ½ of a stride cycle, (i.e. the left hind foot is on the ground when it is assumed that the right hind limb foot is on the ground).    

For The Q to work properly in the 4-beat gaits, it is also important that there be some cadence separation, a short “delay”, between right and left footfall couplets, compared to the time between impacts within each fore/hind foot fall couplet.  In other words, a 1-2...3-4, 1-2…3-4… instead of a 1-2-3-4, 1-2-3-4… beat.  Equal intervals and overlap between all foot falls, as in a true walk, does not allow The Q algorithms to reliably determine beginning and end of hind limb strides.   Although the determination of right from left forelimb strides, because the gyro is on a forelimb, is correct, the determination of right and left hind limb strides at the walk cannot be reliably determined.   However, the walk in general is not a sensitive gait to detect lameness.  

While it may appear that some lameness is better displayed at the walk than at other gaits, this is only because the movement is slow enough for our limited temporal resolution to “pick up” with certainty, whereas the differences present at the trot were more difficult to “see”.  However, because of the higher sampling rate of the inertial sensors, horses that show lameness at the walk will have measurable lameness at the trot.  A hypothetical exception, if it exists, could be some odd pure swinging-limb lameness or other anomaly.  

The Q has been most extensively used and tested in the Missouri Fox Trotter at the foxtrot, the Standardbred at the pace, and the American Saddlebred at the rack. Based on these findings and clinical observations in these and other gaits, the following general guidelines can be made for some common gaited breeds.

Tennessee Walker and Rocky Mountain Horse Running Walk

These ambling gaits do not have a definitive “extra” duration between 2nd and 3rd foot falls, so evaluation will be possible for forelimb but not hind limb lameness.  You may notice that hind limb lameness measured switches sides throughout a trial (stride plots flip back and forth between left and right hind). 

Pictured: Straight line trial from a TWH that was moving somewhere between an amble and a slow pace. Notice that the hind limb stride plots flip sides within the trial. There is also high stride-by-stride variability in amplitude. When this happens, the mean values of Diff Max and Miff Min Pelvis will also be affected, making the side and amplitude of lameness unreliable.


The Missouri Fox Trotter (and the Mangalara Marchador)

These horses are very difficult to evaluate in hand.  They tend to have intermediate, irregular gaits when led.  Regular gait is not usually achieved until the horse is ridden.  Under saddle, side of lameness will be evaluated reliably. However, amplitude of forelimb lameness may be underestimated in some horses.  

The American Saddlebred Rack

Most Saddlebreds display some degree of added excitement when racking.  Also, the rack is usually not held for more than but a brief period in most situations, such that it is not a good gait, in general, to use for evaluation of lameness.  Most Saddlebreds trot nicely however, so this is not a limitation in this breed. 

The Standardbred Pace

When jogging (with or without hobbles), Standardbred Pacers normally move asymmetrically, with a gait that is something between a trot and a pace.  However, they adopt a more stable pace at higher speeds.  So, data is more reliable in the Standardbred pacer when collected at speed, approximately a 2:30 to 2:40 per mile speed. As mentioned above, the hind limb results will measure opposite of true – e.g. a RH lameness will measure as a LH lameness. Forelimb results are true. At these higher speeds, lameness will more frequently be push off type and it is not uncommon for an impact type lameness measured at slow speed to switch to a push off type lameness with increase in speed of movement.  Another thing to keep in mind is that compensatory lameness AIDE statements (suggesting a primary lameness) should be disregarded, as they are based on a contralateral gait.

Paso Finos (Classic, Corto, Largo)

Because the foot fall cadence is 1-2-3-4, similar to the walk, the algorithms used cannot reliably discern side of lameness. Forelimb evaluation will likely be accurate in the Largo, but hind limb results will be unreliable at all three gaits. The Classic is a poor gait to evaluate lameness since the torso is not really moving up and down; only the legs are moving.  

The Icelandic Tolt and Flying Pace

Because the foot fall cadence is 1-2-3-4, similar to the walk, the algorithms used cannot reliably discern side of lameness. Forelimb evaluation will likely be accurate in the Largo, but hind limb results will be unreliable at all three gaits. The Classic is a poor gait to evaluate lameness since the torso is not really moving up and down; only the legs are moving.  



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