Poor performance issues in horses competing at show jumping, dressage and eventing are most commonly due to clinical or sub clinical lameness, occult disease such as gastric ulceration, training and riding issues and/or poor conditioning. Unlike racehorses, most show horses, with the exception of upper level eventers, are seldom asked to exert themselves to their maximum limits.
Sub clinical lameness and bilaterally symmetrical lameness are often difficult to assess by just observing the horse. These types of lameness, however, often lead to performance issues as the horse is reluctant to perform a task that causes pain. For example, a jumper with sore feet may stop before a fence as he knows the landing after the jump is going to hurt! Oftentimes the horse's refusal is thought to be a training issue, when in reality, it is a medical issue. Before assuming a training problem exists, lameness and other disease should be ruled out.
A complete evaluation should include an extensive history, detailed physical exam, evaluation in hand, on the longe and under saddle. Laboratory investigations for certain infectious diseases, neurologic conditions and general health should be undertaken.