The relationship between structure and function is important in the judgement of the horse. Twenty sound riding horses walked and trotted on a treadmill. The movement of the backs of each of the horses was measured using a commercially available movement analysis system. Morphometric, spatiotemporal and kinematic information were correlated to investigate the effect of conformation on movement. Taller and heavier horses seem to have longer thoracic and lumbar backs, and are wider at the pelvis. Horses with longer strides extended and flexed their backs in the caudal saddle region to a greater extent at the walk, but not the trot. Horses with greater angle of L5 tend to extend and flex this region of the back more. At the walk and trot, a long thoracic back results in greater lumbar lateral bending. A negative relationship was found between the curvature of mid-thoracic back and the amount of lateral bending of L1 and L3 and axial rotation of the pelvis at the trot. There are clear relationships between back conformation and movement that may be important to the orthopaedic health of the horse. Further understanding of the relationships between conformation, movement and injury may provide an objective basis for the evaluation of future performance and soundness.