Many horses are affected by lameness each year, with a large number of these horses being examined and treated by veterinarians. According to the 2015 USDA National Animal Health Monitoring System (NAHMS) study on equine management and select equine health conditions in the United States, 67% of horse operations reported one or more lame horses within the past year. In this survey, about 60% of lame horses had lameness examination performed by a veterinarian.
Low-grade lameness is usually of less concern to horses that perform lower levels of athletic function; although early detection and identification of the cause of low-level lameness can lead to earlier treatment, resolution of lameness and return to previous function. Low-grade lameness is more concerning in horses that perform at speed (i.e., racehorses), jump over large obstacles over uneven footing (three-day event horses) or work over extended distances (i.e. endurance horses). Low-grade lameness may indicate the beginning of a larger problem, and if untreated, could lead to a catastrophic injury, which could result in end of career or end of the horse’s life. Thus, good screening tools are needed to identify early, subtle lameness to prevent low grade injury/lameness from developing into a catastrophic injury.
The mainstay of lameness and musculoskeletal injury diagnosis begins with a complete lameness evaluation. However, agreement among veterinarians on the affected leg and degree of lameness is poor for horses with low-grade lameness. Within the past 20 years, horse mounted gait analysis devices have been developed and have been shown to have better accuracy in the identification of low-grade lameness compared to visual examination by experienced veterinarians. Benefits of these systems are ease of use and the ability to be used on the farm.
The Lameness Locator® is one of the first of these systems developed. It is an easy-to-use, accurate system that is currently used by veterinarians around the world. This system is composed of three small sensors that can be easily attached to the horse and provide real-time information about a horse’s lameness by identifying asymmetric head and pelvis movements. This system has the ability to record type of footing and can make comparisons between trials, such as before and after flexion tests and/or blocking.
More recently, additional horse mounted motion analysis systems have been developed. Two such systems are the Pegasus® system and EquiMoves®, both of which were developed in Europe. While these systems are newer, they provide some of the same symmetry indices of the head and pelvis as the Lameness Locator® system. In addition to evaluating movements of the head and pelvis, these two systems also allow evaluation of limb movement since they also include limb mounted sensors. For instance, with the Pegasus®, hock range of motion can be measured. Protraction and retraction, as well as abduction and adduction of all four limbs can also be determined with these systems.
Even more recently, the use of artificial intelligence has provided even more advancements in equine lameness detection and monitoring. A video-based system has been developed for use on a smart-phone, which is called Sleip. This is a subscription based program for veterinarians that allows horse owners to upload videos to a cloud for analysis. This system provides the opportunity for objective follow-up in horses without the need for sensor application.
In addition to improvements in objective lameness assessment, which allows regionalization of lameness, there have also been recent improvements in diagnostic imaging tools that can help with localization of lameness to specific bony and soft tissue structures. Within the past decade, computed tomography has been adapted so that it can be used in standing horses. A CT scan provides 3D imaging of a section of the horse’s body. This type of imaging provides more information about bony structures compared to standard radiographs and with contrast injection, can also be used to image soft tissue structures. The standing CT scanners now available have the same high resolution as previous CT scanners that were only available for use under general anesthesia. Additionally, these new standing CT scanners can be safely used to obtain 3D imaging of the horse’s limbs from the level of the carpus (knee) and tarsus (hock) down through the foot.
In addition to standing CT, positron emission tomography scan is becoming available in horses, which can also be performed in the standing horse. PET allows functional information about bone and/or soft tissue structures within the scanned area, which can indicate if an imaging abnormality is currently active. The PET scan is performed after a radioactive tracer is administered intravenously, similar to a bone scan. The PET scan is combined with another type of imaging (typically MRI or CT) so that the radioactivity can be matched up with specific anatomic structures.
These advances in lameness detection and localization will aid equine veterinarians in early identification of disease processes in horses, which will advance equine welfare, minimize catastrophic injury and prolong the athletic capabilities of horses.
~ Valerie J Moorman, DVM, MS, DACVS-LA, PhD
Clinical Associate Professor Large Animal Surgery and Lameness
University of Georgia College of Veterinary Medicine
