As with the front legs, the technique of the hindquarters is the result of several mechanisms. Hocks start to bend under the weight of the body when the shoulders begin to get up (fig.31). The fetlock is fully extended and often comes flush with the ground with a maximum stretch of the suspensory tendons. Hocks then extend at the point where the neck elongates to pull the fore-hand forward and facilitate the back muscles action (fig. 32). It's the time of the maximum thrust and the levers of the rump open up to get the vertical propulsion.
Stretch of the lumbar sacral joint and release of the levers involved in the vertical propulsion will ensure the quality of hovering above the obstacle.
Dorsolumbar muscles will contract to (slightly) correct the shape of the jump, neck will play its role of balance and hocks will more or less bend to make a "final touch" to the bacule over the fence (fig.33 and 34).
All these mechanisms cause the parabolic shape of the jump, the quality of the elevation of the sacrum, the forwards bascule of the body and the movement of the distal portion of the hind limbs (Hocks and fetlocks) to avoid touching the fence and ensure a good landing.
The assessment will start from "flat" for the horses having a correct vertical boost but not followed by a sufficient rocking motion to shelter a fault, to 'round' for horses highly involving their hindquarters (lumbosacral region, hocks, ankles...) to ensure the bascule over the fence.
More the stifle will be in natural position forward from centerline of the point of the hip to the hock, more the lever opening will be effective in terms of boost.
Wider will be the hock, better it will play its role at the time of the initial push.
As for the front end technique, observation of the gesture of the hindquarters can be affected by "techniques" (polling!) and tricks (tight hind boots) which alter the perception by the horse of its position in space and exaggerate the rocker, the relaxation of the levers of the croup and the role of hind fetlock.
Besides these tricks are of a questionable ethics and that they alter the perception of the natural provisions of the horse (and therefore the conclusions that the breeder can make), they are likely to affect the longevity of the horse by exaggerating the constraints supported by the back at the hover and the forelegs at landing. An exaggerated bascule can cause problems of recovery of balance after the jump.
Precipitation and the instinct of flight can alter the natural gestures of the hind limbs, and to enable it to express themselves, it is essential to get confidence and relaxation of the horse: it comes through the respect of a sufficiently long warm-up phase.
At the end, the breeder will do his best to evaluate the natural predispositions by jumping small repeated fences, by varying the take-off place, before moving on to bigger jumps, with an one or two strides combination.