The hindlimb in walking horses: 2. Net joint moments and joint powers.

The research is a study of the motion of horses’ hindlimbs during walking, specifically looking at the net joint moments and joint powers. It uses data from five healthy horses to explore the dynamics of each hindlimb joint during walking.

Objective and Methodology

• The research was designed to analyze how a horse’s hindlimb joints work during walking. The net joint moments and joint powers were the primary elements studied to understand the biomechanics of a horse’s walk.
• Five horses, all in good health, were the subjects of this study. Their movements were captured and analyzed using synchronous kinematic and force data collection methods.
• Morphometric data that included the size and structure of the horses were combined with the collected movement and force data to calculate the net joint moments across all hindlimb joints during the horse’s walk. This included both the stance and swing phases of a stride.

Results

• The study showed that at the start of stance, when the limb was actively being retracted, the net joint moment positioned on the caudal/plantar side of all hindlimb joints.
• During about 24% of a stride, the net joint moment shifted to the cranial/dorsal side at the hip and stifle, and later during the stance phase at the distal joints. This shift facilitated forward limb movement.
• In the initial half of the swing phase, the net joint moment stayed on the cranial/dorsal side of all joints to actively swing the limb forward. Later, it moved to the caudal/plantar side to reverse the direction of limb motion before ground contact.
• The hip joint was the primary source of energy generation throughout the stride. The tarsal joint assisted the hip joint in both the stance and swing phases, while the fetlock joint assisted only during the stance phase.
• The coffin joint acted as an energy absorber or damper during the stance phase. The stifle joint absorbed approximately equal amounts of energy during both the stance and swing phases.
• When the limb is swung forward and retracted (during the swing phase), the coffin and fetlock joints absorbed energy, indicating that inertial forces drove their movement.

Implications and Future Research

• The study provides a detailed understanding of the dynamics of a horse’s hindlimb during walking, which is crucial for equine locomotion research and veterinary physical therapy.
• The insights gained about the function of different joints during different phases of a stride can be translated into diagnostic practices. Future studies can use these results to detect changes in energy profiles associated with specific soft tissue injuries in horses, aiding in accurate diagnosis and treatment.