Effect of standing tarsal angle on joint kinematics and kinetics.

This research investigates how the standing angle of a horse’s tarsal joint (the joint in the hind leg equivalent to the human ankle) affects the way the joint moves and the forces it exerts. Understanding this could provide insights into various issues such as lameness, performance, and joint degeneration in horses.

Methodology

• The researchers used 16 horses for this experiment. The standing angle of the right tarsal joint was measured while the horses stood with their hind hooves vertically below their hip joint.
• The angles measured were classified as either small ( 165.5 degrees).
• The movements and forces exerted by the tarsal joint during a trot were recorded with reflective markers attached to the joint’s rotation centres. These markers were tracked while the horse trotted at a standardized speed across a force plate.
• The collected data was then used to compute the net joint moments (the turning effect produced by a force) and net joint powers (the rate at which work is done or energy transferred) across the tarsus using a method called inverse dynamics.

Results

• The tarsus of all the horses flexed during impact and extended late into stance. The researchers observed that these movements were stratified based on the standing tarsal angle.
• Horses with larger standing angles exerted less flexion and absorbed less energy at the tarsus during impact than those with intermediate or smaller angles.
• The findings also revealed that horses with larger angles produced lower vertical impulses (change in momentum) than those with smaller angles during stance.
• Additionally, the net extensor moment at the tarsus, which contributes significantly to forward propulsion, was lower in horses with larger standing angles.

Conclusions

• Horses with larger tarsal angles absorbed less impact during the impact phase, potentially making them more prone to degenerative joint diseases.
• However, the lower vertical impulse and extensor moment in these horses could limit their propulsive abilities.
• A positive takeaway is that horses with larger standing tarsal angles might be at lesser risk of developing a condition called plantar ligament desmitis due to lower net joint moments.
• The study determined that a horse’s conformation could significantly impact the functioning and health of the tarsal joint, thereby influencing the animal’s performance and overall soundness (health).