Bitlocker & chkdsk & offline defrag apps

I've learned that offline defrag apps like perfectdisk cannot perform an
offline defrag of a disk encrypted with bitlocker.
What does everyone else use to defrag offline files on a system encrypted
with bitlocker?
Or don't you bother?

I've also been told that bitlocker can also prevent chkdsk from repairing a
drive, has anyone experienced this?

I'm fairly experienced with full disk encryption software & have never
experienced chkdsk being unable to repair an encrypted disk.
To hear that chkdsk cannot repair one encrypted with MS encryption seems
odd.

I know that offline defrag can be a problem in encryption software & have
experienced this myself in other products.

In XP, free compusec worked great & didn;t interfere with chkdsk & offline
defrag, but as yet, no Vista version.

Any thoughts?