It is
But in places where trail is like stairs...with 12-15" high steps... (Much of gsmnp for example) You cant avoid dropping body wt onto lower leg going downhill, because you cant balance over that downhill step while slowly lowering wt.. Unless go down sideways.
. With poles you can, and can go slower with less impact
Invariably people with injuries are going down sideways or even backwards for this reason, to lessen impact.