Lines

 

Observation

The radius are 3 elements constituting the levers of the forelimb and hind limb.

For the forelimb, it includes the scapula (shoulder), the humerus (arm) and the radius (forearm) that goes from the elbow to the knee. Measured by summing the distances ranging from the top of the shoulder blade to the tip of the shoulder, the tip of the shoulder to the elbow and elbow to the top of the knee (fig. 26).
For hind-limb, it includes the Hipbone (basin), and femur which attaches to the pelvic bone at the level of the trochanter and ends in the front by the patella, and tibia (thigh) that connects the femur and Tarsus (Hock). Measured by summing the distances ranging from point of hip to point of buttock, trochanter to the stifle and the stifle joint at the top of the hock. The trochanter is locates about an open hand in front of the point of the buttock towards the tip of the hip.
The angles they form (cf. the shoulder and rump) and their size compared to the rest of the body are evaluated.

 

Characterization

The radius will be "short" or "long" depending on their size relative to the size of the horse measured at the withers and rump and the shape of the figure.
A horse will be told with long front radius if the sum of the lengths of the three radius (A + B + C) is greater than or equal to 95% of the size of the horse at the Withers (D), "rather long" between 88 and 95% of the size, "rather short" between 80% and 88%, and short if it is less than 80% of this size.
The same terminology applies to hind limb (A '+ B' + C), but by measuring the size at the top of the Croup (D) (lumbosacral joint).
The overall impression note is summing up 'forehand' + 'hind hand '.
Attention: the radius are independent of the size at the withers and the extent of the silhouette. Itot du Chateau is a small horse square silhouette, but with long radius!

 

Meaning

The levers allow shoulder and thigh to play their role in locomotion and propulsion at the time of the jump.
The longer they are the easier they will be easy to operate, thus determining a larger amplitude of strides and a stronger boost at the time of the jump.
It seems therefore desirable to favor horses with large radii.

 

Discussion

If they are more efficient, large radii are also more sensitive to 'misuse' and they can become a disadvantage in very rigid or poorly balanced horses. They will then participate to amplify the consequences of the lack of balance and the wrong direction of propulsion when jumping.
As with most of the other characteristics, there again, the assessment must be made by seeing how the horse, or the horse/rider pair, makes them work.