Dr. Sherry Johnson

Known as “the vet truck,” the Equine Sports Medicine (ESM) mobile veterinary clinic provides top-notch care for equine athletes competing in horse shows across the nation. The practice’s two partners, Dr. Alan Donnell and Dr. Dave Frisbie, have dedicated their careers to using evidence-based approaches to treat the variety of orthopedic injuries that top-tier athletic horses experience. Equine veterinarian Sherry Johnson is finishing her sports medicine and rehabilitation residency in conjunction with ESM and the Orthopaedic Research Center of Colorado State University. As part of her work at ESM, Johnson completed a study on Western performance horse lameness that was initiated by past ESM/CSU sports medicine & rehabilitation resident and current ESM associate, Dr. Josh Donnell. She presented this paper at the November 2017 American Association of Equine Practitioners Meeting in San Antonio, Texas.

The study was inspired by the large caseload of Western performance horses evaluated by the veterinarians of ESM, with the goal of providing insight into discipline-specific sources of lameness. The research team evaluated lameness records over 10 years. To be included in the study, the lameness exams had to involve diagnostic blocking to localize the anatomic source of lameness, and include a complete musculoskeletal examination. “We work on a very concentrated population of horses that do a specific job for a living, so we wanted to analyze the results of their lameness exams to see if we might uncover patterns that may help us improve diagnostic and therapeutic options ” Johnson notes, adding that “It made the most sense to categorize horses as all-around western performance athletes or reiners for the purposes of our study. We could then look for any patterns of lameness within the two disciplines.”

Once a lameness case qualified for the study, it was categorized from three perspectives. First, where did the lameness come from, such as the lower limb, hock or stifle. Next, the cases were categorized by which limb(s) was/were affected. Thirdly, to which discipline did the horse belong (reining vs. all around western performance). The study didn’t look at the specific diagnosis of the injury, only the anatomic region of isolated lameness. “If you can identify trends where the lameness comes from specifically in this type of horses, then in future research we can throw our efforts into those specific areas,” says Johnson.

Dr. Sherry Johnson at work on Equine Sports medicine mobile veterinary clinic.

The Study’s Findings

The researchers included 2,677 lameness examinations on 2,521 horses. The average lameness grade among these was 2.2/5. More than half of the lamenesses (56%) were forelimb in nature. Specifically, the foot region was the most commonly diagnosed source of lameness for the horses in this study, even after separating the horses by discipline (reiner vs. all-around western performance horse). This didn’t come as a surprise to the team, but Johnson notes that further studies would be beneficial to take a deeper look into this. “Our study indicates that about 40% of the time, a western performance horse has lameness localized to the forelimb foot region.”

The second most common location was the distal tarsus (hock and hind proximal suspensory region) (16%), followed thirdly by the stifle (9%).

Examining an X-ray during an examination aboard the mobile veterinary clinic.

Johnson says that although this study did not address specific diagnoses, its results reemphasize the role of the farrier. “You certainly cannot discount the role quality shoeing plays in keeping these horses successfully doing their jobs everyday. As a veterinarian, I’m very grateful for the expertise that farriers bring to the table for such a complicated anatomic region. Their work lays the foundation for much of the athletic longevity of these horses,” she says. “Ultimately, just like farriers, if we as veterinarians can understand what a horse does for a living, we will be more successful in treating and rehabbing their injuries.”

Furthermore, the study emphasizes the critical working relationship that exists between farriers and veterinarians. “As with any discipline, collaborating results in the best outcome for the horse,” she says. “and that is what all veterinarians and farriers are going for. Working as a team is a top priority.”

Looking ahead - the next step is to identify the specific diagnosis from these cases. “Now that we have a good bank of horses that blocked to that region, we will likely go back through the records and evaluate any advanced imaging diagnoses to see what exactly was the most common specific injury.” Johnson says. “Common injuries within the foot can include bone bruising, tendon injury or coffin joint osteoarthrosis, but ultimately we need advanced imaging to get us the exact diagnosis.” She looks forward to continuing to research orthopedic issues in western performance horses.