Determining Lameness: Body-Mounted Inertial Sensors Helpful, But No Silver Bullet by Paulick Report Staff|03.15.2023|2:46pm In an effort to detect equine lameness, body-mounted inertial measurement unit (IMU) sensors are placed at strategic locations on a horse's body to record measurements of a horse's gait. This data is then interpreted to determine whether the horse is moving asymmetrically (unevenly), which could indicate lameness. Not all asymmetrical movements detected by these sensors mean the horse is lame, however. Dr. Henry Chateau, with the National Veterinary School of Maisons Alfort Equine Biomechanics and Musculoskeletal Pathology department and France's National Research Institute for Agriculture, explained that many factors can affect the information the sensors glean, including asymmetry in musculature, uneven terrain, or minor genetic differences between left and right side, reports The Horse. “Over-diagnosing” lameness because of interpretation of results from IMU sensors is possible and can have significant financial consequences for horse owners, said Chateau, including unnecessary use of additional diagnostics and time lost in training or competition. Results could also preclude the sale of a horse if interpreted incorrectly. To help determine between true lameness and gait asymmetry, thresholds of asymmetry that determine lameness and soundness are needed. Dr. Chateau and a team of scientists evaluated 224 horses between the age of 2 to 20 for lameness and asymmetry using the EQUISYM system, which places IMU sensors on the head, withers, pelvis, and all four cannon bones. They also had trained experts watch as each horse was trotted in hand in a straight line on asphalt. The experts reported that 62 horses were lame in the left front; 67 were lame in the right front; 23 in left hind and 23 in right hind. The researchers excluded horses that were lame in more than one leg from the study. The 49 horses remaining were deemed “sound” – but not perfectly symmetrical — by the experts, who watched them at the walk and trot in circles on both hard and soft ground in both directions. They also watched them go in a straight line on hard ground and performed flexion tests. After comparing the recorded data from the body-mounted IMUs to what the experts saw visually, the team determined that the threshold values to distinguish soundness from lameness using IMU sensors on a straight line are -7 percent to +10 percent in the front limbs and -7 percent to +18 percent in the hind end. Chateau reiterates that many horses – if not all of them – are asymmetrical to some degree, which is often invisible to the naked eye; this asymmetry is not necessarily a sign of lameness and pain. He expects the thresholds to evolve as more horses complete IMU evaluations, but emphasized that IMU sensors are one tool in a veterinarian's toolkit; they are not a silver bullet to determine lameness. Read more at The Horse.