Kinematics of the distal hindlimb during stance phase in the fast trotting standardbred.

This research investigates the movement dynamics of the lower hind legs of fast trotting Standardbred horses. It specifically studies any changes that occur in this region during the early stage of stance phase, and how these changes can indirectly affect the orthopedic health of these horses.

Study Method

• The study used filming to capture the movement of Standardbred horses while they were fast trotting along a path on an oval dirt track.
• Five consecutive stance phases were analyzed to understand in detail the planar kinematics of the lower end of the horses’ hind legs.

Findings

• Upon examination, the researchers realized that there were rapid changes in the geometry of the distal hind limb during the early stance phase.
• The hoofs were initially braked vertically and shifted direction towards the horse. About 20% of the stance time (ST) was used for the hoof to move forward on the track surface.
• The researchers noticed two deviations at 16% and 29% of ST in the smooth course of the fetlock joint angle – a part of a horse’s leg located above the hoof and below the knee.
• When compared, the tarsal angular joint displacement, situated between the fetlock joint and the horse’s body, was smoother throughout the stance phase.
• The segment angular velocity was greatest in the proximal pastern segment (located between the fetlock joint and the hoof) while the metatarsus was nearly completely braked in its forward rotation during the early stance.
• The tibial angular velocity was smoother and greater than that of the metatarsus. It also found that the initial vertical braking of the hoof was linked to the rapid rotation of the proximal pastern segment.
• There was a decrease in the angular velocities of the metatarsal and proximal pastern segments as the hoof was braked horizontally. There was also an increase in the angular velocity of the tibial segment along with horizontal braking of the hoof.

Conclusions

• The study concluded that the horizontal and vertical braking of the hoof had an impact on the disto-proximal braking (braking from tip to top) of the segments of the distal hind limb, during the early stance phase.
• The rapid changes in the distal hind limb come with implications for the internal forces of the limb.
• These changes are believed to have important implications for the orthopedic health of Standardbred trotters, especially in relation to conditions such as lameness which are thought to be induced by excessive and repetitive load and movement on the fetlock joint and hock joint during their early stance.