Does the muscle start separating from the bone in atrophy?

Loose, not separate: Muscle atrophy does not affect the enthesis (the attachment of muscle to bone), since most of the contractile tissue transitions into tendon at the bony attachment site. Tendon is more resilient and does not atrophy in the same way as muscle. The muscle wasting can cause it to feel loose and floppy, however, and bony prominences may stand out more since the overlying muscle has atrophied.