Mystery Horse Lameness? Exploring Rein Lameness

I call it the lameness that is not really lameness. Sometimes a horse develops an unexplainable hitch in his movement that leads to much head scratching from vets who after an array of diagnostics find no clear answers. The horse is described as being not quite right but beyond that there is no reason or treatment.
This mystery lameness that produces an inconsistent limp during one or more gaits is often what we call rein lameness. It is a disrupted gait pattern owing to muscular tension or imbalances that have reached a point of negatively affecting motion through the spine. The term rein lameness originated from the frequent occurrence of horses made sore from riders with too much rein pressure. It does not however only originate from tight reins. In fact I observe it most often in recreational riders horses ridden on loose or inconsistent rein contact.

The following is a simplified description of the development of this condition. In good healthy movement the horses torso channels energy forward from the hind legs. It both creates and stabilizes the force of the hind limbs swinging forward each stride. Tension in the back or abdominals disrupts the synergy needed between these two muscle groups in order to play this role. The disruption in their interplay due to this tension and imbalance causes the horse to shortstride with one hind leg. This causes his trot rhythm to be noticeably uneven or it may cause an actual limp. While it can sometimes be observed in