Limb movement adaptations in horses with experimentally induced fore- or hindlimb lameness.

This research focused on understanding how horses adapt their movement when one of their legs is artificially made lame. The study looked at how the horses changed their joint movements and hoof patterns to compensate for the lameness, providing insight for identifying potential indicators for leg lameness in horses.

About the Experiment

• The researchers studied the movements of 11 Dutch Warmblood horses (a breed known for its athleticism) that had no clinical indications of lameness.
• A locomotion analysis system, CODA-3, was used to accurately record the kinematics (the branch of physics dealing with motion) of the horses. Each horse was made to walk and trot on a treadmill at set speeds.
• To induce lameness in the horses, an experimental model was used that applied pressure to the hoof sole, recreating physical conditions that could cause natural lameness.

Research Findings and Analyses

• The research recorded and analyzed several indicators including joint angle patterns, hoof movements, and trajectories. These data were further examined and compared using a statistical method known as a two-way analysis of variance to identify significant variations.
• The results showed a decrease in hyperextension of the fetlock joint (the joint between the hoof and the long bones in the horse’s legs) and the flexion (bending) of the coffin joint (the last joint of the horse’s leg before the hoof) during the stance phase in the lame leg. This happened regardless of whether the artificial lameness was induced in the forelimbs or hindlimbs, and at both gaits (walking and trotting).
• In contrast, there was an increase in the same joint movements in the non-lame legs, suggesting that the horses were compensating for the lameness by adjusting movements in their healthy legs.
• When the horse’s state of lameness intensified the shoulder joint and even more so the tarsal joint (the horse’s equivalent to the human ankle) of the lame limb showed increased flexion, again this indicates an adaption to help carry the load imposed by lameness.
• Lameness also affected the retraction of the forelimbs and protraction of the hindlimbs, i.e., the retraction of the non-lame forelimbs decreased during forelimb lameness at a walk, and the protraction of the lame hindlimb decreased during hindlimb lameness.
• The arcs made by the hooves of the lame limbs were lower than those of non-lame limbs. This was either due to an increase in hoof height in the non-lame limb during forelimb lameness or a decrease in height in the lame limb during hindlimb lameness.

Conclusion

• The researchers concluded that the patterns in distal joints (joints farther from the center of the body), such as the fetlock and coffin joints, reflect the way horses redistribute the loadings of their limbs when dealing with lameness.
• The adjustments observed in the proximal joints (closer to the center of the body), particularly the shoulder and the tarsal joints, showed that these joints act as load dampers, reducing the peak forces on the lame limb.
• The decrease in hyperextension of the fetlock joint and the flexion of the coffin joint showed potential as the most sensitive indicators for lameness in both fore- and hindlimbs.