Equine poor performance: the logical, progressive, diagnostic approach to determining the role of the temporomandibular joint.

Poor performance is an ambiguous term used frequently by people in the horse industry. It means different things to different people, depending on the breed, discipline, or problem being discussed. There are myriad reasons that a horse may fail to achieve the expectations put upon it or, having achieved those goals, begin to falter. Equine temporomandibular joint (TMJ) disease is beginning to be reported as 1 such cause of poor performance. Despite this, in certain disciplines, it has become the trendy diagnosis, and a logical approach to the diagnostic workup is often lacking. Many of the clinical signs attributed to TMJ abnormalities can be readily explained by other more common problems. This ambiguity is compounded by a lack of extensive scientific evidence linking TMJ-related disease to behavioral or performance changes. Despite this fact, the equine TMJ has been reported to be a cause of poor performance, and while rare, it should be included in a differential diagnosis list, albeit one of exclusion. The purpose of this article is to describe a logical, stepwise approach to excluding common causes of poor performance before investigating the potential role of the TMJ in cases of poor performance.