The forelimb in walking horses: 2. Net joint moments and joint powers.
Authors: Clayton H M, Hodson E, Lanovaz J L
Journal: Equine veterinary journal
Summary
# Editorial Summary Clayton and colleagues used inverse dynamics analysis—combining high-speed video, force plate data, and limb measurements—to quantify the net moments and power generation across equine forelimb joints during walk, revealing a functionally specialised kinetic chain where the elbow emerges as the primary energy generator whilst proximal and distal joints adopt distinctly different mechanical roles. During stance, palmar (flexor) moments dominated at the carpus, fetlock and coffin joint, whilst the shoulder exhibited disproportionately high moments relative to other joints; notably, the forelimb as a whole absorbed energy during both stance and swing, creating a paradox resolved by the elbow's unique capacity for net energy generation. The carpus functioned primarily as an alignment mechanism with minimal energy exchange except for a brief flexor-side burst initiating breakover, whilst the fetlock operated elastically to store and recover strain energy and the coffin joint dampened impact forces before actively assisting breakover initiation. The magnitude of joint power during swing decreased progressively from proximal to distal segments, suggesting inertial forces rather than muscular effort drive distal joint motion during this phase. For equine professionals, these findings establish a biomechanical framework for understanding how horses redistribute loading and energy demands across forelimb joints when compensating for lameness—information particularly valuable for targeting rehabilitation, assessing movement asymmetries, and predicting secondary injury patterns in different forelimb conditions.
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Practical Takeaways
- •Understanding that the elbow drives forelimb energy generation can inform therapeutic strategies for forelimb lameness—strengthening or addressing elbow dysfunction may be more critical than focusing solely on distal structures.
- •The fetlock's elastic function and carpus's active role in breakover initiation suggest these joints require adequate range of motion and proprioceptive feedback; farriers should consider breakover mechanics when addressing chronic forelimb issues.
- •Lame horses likely redistribute energy generation and absorption between joints as compensation; clinical assessment should examine proximal joints (especially shoulder and elbow) for dysfunction that may drive distal lameness patterns.
Key Findings
- •The elbow is the primary site of energy generation in the equine forelimb during walk, maintaining limb extension during stance and driving protraction/retraction during swing.
- •The shoulder and coffin joints function as energy dampers during stance, with peak shoulder moments considerably higher than all other forelimb joints.
- •The fetlock stores and releases strain energy elastically during stance, while the carpus plays a minor role in energy absorption/generation but actively initiates breakover through flexor work.
- •Distal joint powers decrease in a proximal-to-distal sequence during swing phase, with distal joints appearing to be driven primarily by inertial forces rather than active generation.