Perhaps you could direct this question to Ms. Zeigler, who seems to have lots of knowledge on horse gaits, etc. A recently published article on Foxtrotting show horses said that when the show Foxtrotter walks, and foxtrots, it does not bend at the knee. Is that possible ? It seems that a stiff front leg would not give as smooth a ride, and would also subject those horses to be "stumbley" on the trail, or flat dangerous in rough terrain. It seems that in the long run, this type of movement would be detrimental to the breed as a trail and pleasure riding horse. Your thoughts....
In answer to the question on bending the knee at the fox trot. Of course they bend at the knee, they could not move their legs if they did not! I believe that what the writer was trying to say was that Fox Trotters do not have high knee action, and tend to reach "out" rather than "up" with their front legs. This type of leg use in front is different from that of the typical Tennesee Walker or Saddlebred, for example, but similar to that of a Tbred or good moving Quarter Horse.
For this reason, good conformation in the front quarters of a Fox Trotter should include a long, well sloped shoulder and a long, more horizontal than vertical humerus. This predisposes to reach rather than action. In a TWH, however, an upright shoulder and more vertical humerus are desireable because they will predispose to high, short action in front.
The humerus bone is; " the bone running from the front point of the shoulder to the elbow"