Our entire congregation kneels from after the Sanctus
to the Amen except those of us in the choir....
Can I assume that although we are not crippled
we should remain standing while we sing?
lol.... Yes you may....
The choir has a ministry at various times during
the Liturgy.... Therefore, when singing, since you
can perform your ministry better when standing,
you are exempt.
Just as the priest is exempt from kneeling
because of his ministry, so is the choir.