Net joint moments and powers in the equine forelimb during the stance phase of the trot.

This research focuses on studying the net joint movements and sequences in trotting horses, aiming to provide comprehensive data that would further our understanding of the mechanics and energy consumption during movement, which could prove useful in diagnosing and addressing lameness in horses.

Research methodology

• The data for the research was gathered from six Warmblood horses while they trotted. The focus was on the right forelimb of each horse.
• Time-aligned kinematic and force plate data was collected, mapping out the movements in three dimensions.
• The 3D data was then simplified into a sagittal plane (a vertical plane passing from front to rear).
• This simplified data was merged with vertical and longitudinal ground reaction forces, also taking into consideration each segment’s morphometric data. This allowed for the calculation of net joint moments (or the net force applied at each joint) in the sagittal plane across various joints: shoulder, elbow, carpal (equivalent to the human wrist), metacarpophalangeal (fetlock), and distal interphalangeal (coffin).
• The joint mechanical power, or the product of joint moment and the angular velocity of the joint, was generated from the calculated net joint moments.

Key Findings

• Each joint exhibited notable and recurring patterns in the net joint moments and joint powers.
• During the majority of the stance phase, the net joint force was on the caudal/palmar side (in mammals, the back side of the forelimb) of all joints, except for the shoulder.
• Unlike the other joints, the coffin joint appears to absorb energy, peaking at 74% of the stance phase, which coincides with the maximum longitudinal propulsive force.
• The fetlock joint acts as an elastic spring, absorbing energy in the first half of the stance phase and releasing it during the second half, demonstrating a characteristic energy storage and release pattern. This, however, was not observed in the carpus, which seemed to have little role in energy absorption or propulsion.

Implication of Key Findings

• Rather than generating or absorbing energy, both the elbow and shoulder joints showed phases of elastic energy storage and release during the middle part of the stance phase. The shoulder, however, did demonstrate a propulsive function during the latter part of stance.
• The net energy generation at the shoulder joint closely matched the energy absorption at the coffin joint.
• Understanding the normal function and dysfunction of these different anatomical structures, and how they interact mechanically, is a major step forward in understanding equine lameness and could be a useful tool in diagnosing it.
• This information can also be useful in interpreting clinical findings in terms of mechanical deficits in the context of specific gait pathologies, enabling more effective treatments and interventions.