drop_down
1. [ verb ] "He fell down to his knees
Synonyms: fall_down
Related terms: descend prolapse
2. [ verb ] fall or drop to a lower place or level
Synonyms: sink drop
Examples:

"He sank to his knees."

Related terms: rise change_posture sag drop_open sag drop slump
Similar spelling:   drop_dead
  draped
  dropped