Radiographs are commonly used to assess the presence of pathology in imaged joints and how that might impact a horse’s performance. It is well established that yearling Thoroughbred racehorses are subjected to radiographic review of multiple joints prior to sales. Now, a similar strategy of repository radiographs is being employed for Quarter Horses used for cutting.
Collaboration among faculty at Colorado State University’s Equine Orthopedic Research Center and College of Veterinary Medicine and Biomedical Sciences examined the association of radiographic findings with cutting horse performance and money earnings [Barrett, M.F.; McIlwraith, C.W.; Contino, E.K.; Park, R.D.; Kawcak, C.E.; Frisbie, D.D.; zumBrunnen, J.R. Relationship between repository radiographic findings and subsequent performance of Quarter Horses competing in cutting events, JAVMA vol. 252, no. 1, Jan 1 2018; pp. 108–115].
The study reviewed imaging from 458 yearling and 2-year-old Quarter Horses to determine the importance of a variety of radiographic “lesions” on performance, following the horses into their fourth year. The research study concluded that, in general, radiographic abnormalities of competitive Quarter Horses used for cutting were not significantly associated with subsequent performance.
However, there were a few lesions that did impact performance outcome:
- osteophytosis of the dorsoproximal aspect of the middle phalanx of the hind limb
- osteophytosis of the distal aspect of the tarsal joint, particularly if mild Grade 1 or 2
The researchers were surprised that mild tarsal lesions could impact performance more than more severe tarsal lesions. Previous studies of yearling Thoroughbred racehorses with osteophytes or enthesophytes of the centrodistal and tarsometatarsal joints demonstrated that they were less likely to start a race. However, only 9% of evaluated cutting horses were diagnosed with Grade 3 or 4 tarsal osteophytes and so represented a low statistical number of those in the study.
Another consideration is that those horses with more advanced tarsal osteophytosis would have likely been treated with intra-articular medication, and such therapy might contribute to improved performance.
Interestingly, in this study, cutting horses with hind limb pastern joint osteophytes were three times as likely to earn money as 4-year-olds compared to horses lacking this radiographic finding. The authors suggested that stresses on this joint from pivots related to training could induce remodeling and radiographic changes.
Also of interest, they found that lameness attributable to radiographic findings of the middle femoral condyle of the stifle joint did not impact performance and earning ability in the early years of a cutting horse’s career.
The authors stressed that joint soundness or pathology is only one aspect of a horse’s ability to perform. Other factors that affect performance outcome include training methods, horse temperament, innate talent, genetic influences on musculoskeletal structure and metabolic stamina, as well as the variability in cattle behavior.