Abstract
Recent studies evaluating horses in training and considered free from lameness by their owners have identified a large proportion of horses with motion asymmetries. However the prevalence, type and magnitude of asymmetries when trotting in a straight line or on the lunge have not been investigated. The aim of this study was to objectively investigate the presence of motion asymmetries in riding horses in training by identifying the side and quantifying the degree and type (impact, pushoff) of forelimb and hind limb asymmetries found during straight line trot and on the lunge. In a cross-sectional study, vertical head and pelvic movement symmetry was measured in 222 Warmblood type riding horses, all without perceived performance issues and considered free from lameness by their owners. Body-mounted uni-axial accelerometers were used and differences between maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) vertical displacement between left and right forelimb and hind limb stances were calculated during straight line trot and on the lunge. Previously reported symmetry thresholds were used. The thresholds for symmetry were exceeded in 161 horses for at least one variable while trotting in a straight line, HDmin (n = 58, mean 14.3 mm, SD 7.1), HDmax (n = 41, mean 12.7 mm, SD 5.5), PDmax (n = 87, mean 6.5 mm, SD 3.10), PDmin (n = 79, mean 5.7 mm, SD 2.1). Contralateral and ipsilateral concurrent forelimb and hind limb asymmetries were detected in 41 and 49 horses, respectively. There was a linear association between the straight line PDmin values and the values on the lunge with the lame limb to the inside of the circle. A large proportion (72.5%) of horses in training which were perceived as free from lameness by their owner showed movement asymmetries above previously reported asymmetry thresholds during straight line trot. It is not known to what extent these asymmetries are related to pain or to mechanical abnormalities. Therefore, one of the most important questions that must be addressed is how objective asymmetry scores can be translated into pain, orthopedic abnormality, or any type of unsoundness.
Highlights
Orthopedic diseases constitute the most common group of health problems in riding horses and remain one of the most common causes of interrupting the athletic careers of horses [1,2]
For straight line trot there were, 30 ±12.3 strides evaluated per trial
A major proportion of horses in regular training show motion asymmetries of similar magnitude to asymmetries found in horses examined and treated for lameness
Summary
Orthopedic diseases constitute the most common group of health problems in riding horses and remain one of the most common causes of interrupting the athletic careers of horses [1,2]. The clinical lameness examination has been the prime tool to detect and investigate orthopedic diseases for decades, but currently applied clinical methods appear rather insensitive to subtle pain and pathology with resulting small changes in motion symmetry [4,5,6]. The non-lame horse shows a symmetric sinusoidal motion pattern of head and pelvis which undergoes systematic changes when loading of the limbs changes, for example as a result of lameness [8,9,10]. The differences in maximum and minimum position of head or pelvis between left/right stances (HDmin, HDmax, PDmin and PDmax) are examples of symmetry measures commonly used for quantification of lameness and are directly linked to the underlying changes in limb loading and propulsion [10,11]. Only few studies have correlated degree of clinical lameness to the biomechanical results of symmetry measurements. It is essential to improve our knowledge on how objectively measured asymmetry scores can be translated into pain, dysfunction, orthopedic abnormalities, or any type of unsoundness
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