hock and stifle work together. If the hock flexes, the stifle flexes, and if the hock is extended, the stifle must extend as well.
Rupture of the peroneus tertius is defined as one hundred percent strain of the peroneus tertius muscle and or tendons. In common terms this is a complete tear of the peroneus tertius muscle.
There are three types of trauma that can lead to rupture of the peroneus tertius.
The first pattern of trauma is the forceful
of the hock
The second pattern is the repeated
of the stifle
The third pattern is trauma to the cranial aspect of the
or the dorsal
surface of the hock.
Forceful hyperextension of the hock occurs when there is sudden retraction of the foot during the propulsion phase of stride causing a tensile force that exceeds the ability of the peroneus tertius to stretch. Repeated hyperflexion of the stifle occurs when the hip muscles fatigue, decreasing the movement of the hip and sacroiliac joint. To compensate, the hind limb is extended further behind the body by the hamstring and middle gluteal. This causes micro-tearing of the peroneus tertius with every stride. Micro-tears reduce the elasticity and strength of the peroneus tertius and eventually the force of the hyperflexion of the stifle becomes greater that the tensile strength of the muscle causing rupture of the peroneus tertius. The third pattern of force causing rupture of the peroneus tertius is trauma to the cranial or dorsal aspect of the gaskin or hock. This trauma cuts fibres of the muscle or tendons of the peroneus tertius weakening the musculotendinous unit to the point that the weight of the limb exceeds the tensile strength of the fibres that remain intact. Occasionally the trauma is sufficient to cause one hundred percent strain of the peroneus tertius without any attempt at movement. events are predisposed to forceful hyperextension of the hock. Those horses involved in racing, cutting, polo, or jumping events tend to forcefully extend the hock in the normal course of their activities, if the foot slips caudally while the horse is in the process of forcefully extending the hock the joint hyperextends and strains the muscle. Slippery footing increases the risk of forceful hyperextension of the hock during activities at speed. Horses involved in
horses pulling heavy loads or ploughing hard ground &
horses are
predisposed to repeated hyperflexion of the stifle. racehorses are also predisposed to hyperflexion of the stifle as they tend to have sickle hocks, are gaited, and tend to be involved in moderately long races.
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