Source : Webster's Revised Unabridged Dictionary (1913)

Painless \Pain"less\, a.
   Free from pain; without pain. -- {Pain"less*ly}, adv. --
   {Pain"less*ness}, n.

Source : WordNet®

painlessly
     adv : without pain; "after the surgery, she could move her arms
           painlessly" [ant: {painfully}]