Evaluation of equine locomotion during different degrees of experimentally induced lameness. I: Lameness model and quantification of ground reaction force patterns of the limbs.

Force plate data from walking horses were used to evaluate the locomotion of a group of six horses during experimentally induced lameness in a forelimb or a hindlimb. By tightening or loosening screws in modified horseshoes the resulting pressure pain on the sole enabled induction and release of three different degrees of supporting lameness within a period of 2 h. The ground reaction force (GRF) patterns of the different recording sessions were compared with control data of the same horse as well as with the 'standard' horse data using a quantitative evaluation procedure involving 93 GRF parameters. Clinically mild and moderate lameness at the walk could be distinguished by applying the H(orse)INDEX method, using 'standard' GRF data of horses of the same breed. Even subtle changes (clinically mild lameness at the trot but no lameness visible at the walk, and nerve blocking of moderate lameness at the walk) could be demonstrated objectively using an adapted quantification procedure (the C(ontrol)INDEX method), if control GRF parameters of that horse were obtained before lameness was present.