The hindlimb in walking horses: 1. Kinematics and ground reaction forces.
Authors: Hodson E, Clayton H M, Lanovaz J L
Journal: Equine veterinary journal
Summary
# Editorial Summary: Hindlimb Kinematics and Ground Reaction Forces in Walking Horses Hodson, Clayton and Lanovaz's 2001 investigation established foundational reference data on how hindlimb joint motion correlates with loading forces during walk, examining eight strides from five sound horses using synchronised video (60 Hz) and force plate (2000 Hz) capture. The first 10% of stride revealed rapid loading accompanied by coordinated stifle, hock and coffin joint flexion with fetlock extension—a pattern directly reflected in the biphasic vertical force curve with its characteristic dip. Hip flexion and extension drove entire-limb protraction and retraction respectively, whilst mid-stance hock extension occurred independently of the braking and propulsive forces, suggesting longitudinal loading is not simply a kinematic consequence. The finding that total braking impulse precisely balanced propulsive impulse across the full stride cycle provides a quantitative baseline for assessing gait asymmetry in lame horses. For practitioners, these relationships between joint angles and force distribution offer a mechanistic framework for interpreting why certain lameness presentations affect specific joints preferentially, and this work has subsequently enabled clinicians to identify abnormal loading patterns that precede visible gait alterations.
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Practical Takeaways
- •Understanding normal hindlimb loading and joint coordination patterns in sound horses provides a baseline for identifying lameness-related deviations during clinical evaluation
- •The bimodal vertical force pattern and fetlock mechanics are key indicators of normal loading; abnormalities here may reflect joint pain or proprioceptive deficits
- •Hip-driven limb protraction and the coordinated stifle-tarsal motion during swing are essential for normal stride mechanics; loss of coordination may indicate muscle or neurological problems affecting hindlimb function
Key Findings
- •Hindlimb loading occurs rapidly in the initial 10% of stride with concurrent stifle, tarsal and coffin joint flexion and fetlock extension
- •Vertical ground reaction force shows a bimodal pattern that correlates with fetlock joint angle changes throughout stance
- •Hip flexion/extension drives protraction/retraction of the entire hindlimb, with maximal protraction before swing end and maximal retraction at breakover
- •Stifle and tarsal joint flexion cycles are coordinated during swing phase to raise the distal limb during protraction