The Role of Flexion Tests in Lameness Examinations: What's the Evidence?

Assessing the presence and diagnosing the cause of lameness in horses has been a challenge for veterinarians since the earliest days of equine medicine. Flexion tests have long been an integral part of this assessment of lameness in horses. Flexion tests are procedures in which joints or joint complexes are stressed and the horse then evaluated for the appearance or an exacerbation of lameness in the limb. The first recorded evidence was provided by Hertwig (1850), who described a hindlimb flexion test to help identify the presence of osteoarthritis of the distal hock joints. In clinical practice, flexion tests are currently used to help localise pain causing lameness but also as a risk-assessment tool in prepurchase examinations to predict potential or future lameness problems.

It is important to realise that there are very definite limitations to the specificity of flexion tests and to the conclusions that can be drawn in relation to localisation of limb abnormalities. It is virtually impossible to stress a single articulation without also stressing other structures through attached ligaments and tendons. In the hindlimb for example, the reciprocal apparatus does not allow flexion of one joint, without concurrent flexion of every other articulation of that limb. [...]