It depends on the knee problem. Problems in the cartlidage can make it
extremely difficult to have the knee bent as much as required by
posting - even it you do it right. Same for an ACL or MCL problem. Some
people just can't comfortabely ride the trot for a long period of time.
You are right if you knees are relatively healthy to start with and
they start to hurt - time to check how you are riding. But if they are
trashed to start with - sometimes a gaited horse is the best option.
I don't have an arab myself, although I love
the breed. My knees can't handle that trot anymore.
You know, I've heard this complaint a lot before. My understanding of
how to post is *not* that you lift yourself out of the saddle, but that
you allow the horse's motion to lift you just as far as it wants to
lift you, and you settle down, using flexion of the ankles, knees, hips
and back to smooth that descent. So the knee joints just shouldn't
have to do all that much work - seems to me if they are, then there's
too much effort going into the posting. Each person's joints will be
what they will be, but I have found over the years that when I have
joint pain from riding, it's time to reassess my riding form.
