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Lameness diagnosis in the horse can be subjective and difficult especially when mild. There are lameness locator machines that have been developed to reduce the possible bias that exists in lameness diagnosis, which are a great tool for the equine clinician, however they are far from being able to replace his or her expertise.
Some equine veterinarians love lameness while others hate them… but all must deal with them sooner or later in their careers. Why is lameness diagnosis such a challenging area of our daily routine? Because lameness detection is as much a science as an art. Traditional lameness examinations involving physical examination, trotting up the horse in the straight or circle over different surfaces, with or without a rider and nerve/joint blocking, is not exact . Studies has shown that the more experienced the clinician, he or she is better at detecting it and that there is usual disagreement between veterinarians examining the same case [2,3]. Even the speed of trot can influence the outcome  and even widely used diagnostic methods, such as flexions tests, can also be variable between horse genders . In summary, lameness detection can be subjective specially when the lameness is subtle .
The solution is a machine capable of detecting very small differences in vertical movement between contralateral limbs. These “lameness locators” have got IMUs sensors equipped with accelerometers and gyroscopes that are attached to the tack or horse with double sided tape or Velcro and feed data to a laptop [7-10]. In seconds, the machine measures the amount of vertical asymmetry in millimeters and show where the feet are landing with respect to a center point. These lameness locators are more effective at detecting subtle lameness than veterinarians. Lameness locators objectivize the lameness by indicating the lame limb and giving the lameness a number.
The lameness locator is quite portable and fits in a small suitcase or rucksack, making it easier to use in the field. The sensors are easy to put in place and do not leave a mark after
removing them. To obtain the best readings, the horse should be trotted by a competent handler in a straight line on a hard, even surface that allows for at least 25 strides or for the lameness to stabilize . The lameness locator facilitates lameness diagnosis by a wider range of types of vets. These include new graduates who are not confident in their abilities yet , veterinarians who do not deal with equine lameness on a daily basis, for example, mixed practice vets who do more small/large animals with the odd equine patient thrown to his/her caseload; but also experienced equine veterinarians who deal regularly with lameness but want to confirm their findings.
Lameness locator readings are also useful when referring a case or having a consultation with a colleague, as it is known that agreement between clinicians can vary considerably specially if the lameness is mild . When the lameness is objectively measured, it can be compared and its progression assessed on other occasions or by another veterinary clinic. The only requirement would be to be aware of the slight difference of reading between brands of lameness locators . The lameness locator data can be incorporated into the lameness examination routine and even flexion tests can be performed and evaluated with it positively .
In my experience, every horse that is examined for any condition should be assessed, if possible, by a lameness locator, on more than one occasion, to have a “gait signature” on record for that individual. This could be useful later when the patient does come back to the clinic with a lameness complaint. The veterinarian will have to take into consideration the natural day to day, week to week variations of gait in horses . Another potential use of the lameness locator would be to monitor rehabilitation of conditions that need increasing amounts of controlled exercise, for example horses recovering from
tendonitis. Where a small increase in asymmetry could indicate
that a reduction in exercise level is needed.
The machine can only give an indication of which limb is lame,
giving a measure of asymmetry but cannot tell which anatomical
part of the limb itself is painful or responsible for causing the
lameness. Here the knowledge and diagnostic abilities of the
veterinarian are vital: with diagnostic analgesia, used to pinpoint
source of pain, and usual imaging such as ultrasonography,
radiography and MRI being used to give more insight to the
investigation. Recently data from the withers measured by
the lameness locator has proven useful in the diagnosis of
complicated, multi-limb lameness . The veterinarians
using the lameness locator have to take into consideration that
certain surfaces reduce asymmetries more than others [18,19];
that different breeds of horses/disciplines allow for more
asymmetry (higher threshold) than others, so measurements
have to be interpreted with care until these thresholds have been
The take home message is that the lameness locator cannot
replace the equine veterinarian yet but should be used routinely
in every horse that is seen for lameness. It is another invaluable
tool for lameness diagnosis in the arsenal available to the
clinician. Ideally every horse should have a record of its “gait
signature” while sound. Finally, it is the equine veterinarian,
thanks to his or her knowledge, training and experience, who has
to make the final decision on the numbers shown by the locator if
they are a lameness or just an asymmetry .
Many thanks for all the support given by Dr Thilo Pfau and
Prof Renate Weller from the Structure and Motion Laboratory
at the RVC; to Dr Amy Barstow, to the trainers and staff of the
Singapore Turf Club, special Dr Koos van der Berg for all their