Defining normal three-dimensional kinematics of the lower forelimb in horses

Abstract

Summary Although the equine metacarpophalangeal joint is frequently damaged, there is a scarcity of data concerning the three-dimensional kinematics of this joint. Thus, the purpose of this study was to define normal three-dimensional kinematics of the distal forelimb. Six mature Thoroughbreds were adapted to a high-speed treadmill and filmed at awalk (2.0 m/s), trot (4.0 m/s), and left-lead canter (7.0 m/s). An autodigitizing videographic system was used to collect and analyze the three-dimensional kinematic data. Retroreflective markers were placed on the left forelimb at approximate centers of rotation of the carpal and metacarpophalangeal joints and at midpoints of the radius, third metacarpal bone, and hoof. The measures made during the experiment included the angle the fetlock and hoof made with the ground in three dimensions (the XZ, YZ, and XY planes), range of motion of the fetlock joint, limb acceleration and velocity, stride length, and stride frequency. The average joint angles in the XZ plane at impact were 134.6°, 140.6°, and 151.7°, and at lift-offwere 69.6°, 81.2°, and 88.9° for the walk, trot, and canter, respectively. In the YZ plane, average impact angles were 99.2°, 97.2°, and 100.3°, and lift-off angles were 96.4°, 96.6°, and 95.5° for the walk, trot and canter, respectively. In the XY plane, average impact angles were 136.4°, 130.3°, and 136.3°, and lift-off angles were 163.2°, 168.4°, and 173.6° for the walk, trot and canter, respectively. Total range of motion of the fetlock joint was 50.3° at the walk, 52.1° at the trot, and 56.0° at the canter. Average acceleration values of the fetlock joint determined at peakprotraction were -90.3, -121.9, and -201.6 and at the end of retraction were 112.0, 126.1, and 238.7 m/s 2 for the walk, trot, and canter, respectively. The average stride frequencies for the walk, trot and canter were 0.98, 1.44, and 1.88 Hz, respectively. The average stride lengths for the walk, trot and canter were 2.21, 2.72, and 3.79 m, respectively. These data will be used to build a base on normal three-dimensional kinematic patterns of the distal forelimb of the horse moving at the walk, trot, and canter on a high-speed treadmill.