Both horse owners and veterinarians spend a lot of time observing horses for lameness, but not all observers perceive lameness the same. Sometimes this is because of a less than clear understanding of equine biomechanics. Researchers such as Florian Buchner, DMV, PhD, an equine orthopedic surgeon at the University of Vienna, are seeking to better explain how the horse moves when sound and lame. During the 2005 American Association of Equine Practitioners Convention held Dec. 3-7 in Seattle, Wash., he discussed lame forelimb and hind limb movements and orthopedic shoeing.

“If loading (supporting limb lameness) or moving (swinging limb lameness) of the limbs causes pain, horses change limb timing, stride pattern, and limb joint movement pattern in all limbs to cope with the pain,” he said.

Some of his observations of lame horses are as follows:

• Stride duration decreases, and there is an increased stride frequency.


• Stance duration is longer, symmetrically (for both lame and sound sides).


• There is a marked decrease in the length of the suspension phase.


• The kinematic pattern of limb movement reveals two different spring-like systems. The distal (lower) spring consists of the fetlock and the coffin joint and represents, by its passive nature, the loading pattern of the limb. The proximal (upper) spring consists of the shoulder/elbow joints or the tarsal/stifle and hip joint complex. The proximal spring can adapt actively to lameness by increasing flexion during midstance in the lame limb, which smooths out the loading of the painful limb. The distal joints indicate reduced loading in the lame limb by decreased midstance excursions (i.e., reduced hyperextension of the fetlock joint and reduced flexion of the coffin joint).


• A lame limb is loaded less than its sound counterparts, but the sound limbs are not overloaded (to the point of failure). There is greater loading of the contralateral (on the other side) limb, but no change in the diagonal limb, and even a small decrease in the ipsilateral (on the same side) limb.


• Fetlock hyperextension during midstance decreases with increasing lameness. This decrease is about 8° for a 2/5 forelimb lameness. In the sound contralateral forelimb, a compensatory increase in hyperextension can be seen; however, the change is smaller (about 2°) than the reduction in the lame limb.


• With increasing lameness, maximal coffin joint flexion during the stance phase in the lame limb is reduced, whereas maximal joint flexion in the contralateral limb is increased.


• Carpal or tarsal joint lameness is characterized by reduced carpal/tarsal flexion during the swing phase.


• There is a significant reduction or absence of the suspension phase after the lame stance. This stance phase of the lame limb is not shorter than stance duration in the same limb without lameness. During this painful stance phase, the sound limb is earlier and further protracted (brought forward), compensating for the missing flight phase (suspension phase) after the lame stance

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