Arrington has suffered a fracture to her back, broken ribs and a partial collapse of a main artery in her leg.
She will have undergo surgery and will require more procedures and weeks of recovery, CNN reports.
Arrington is alert and recovering at the Medical University of South Carolina and her family is by her side.
President Donald Trump expressed his sympathies to Arrington via Twitter.
Arrington defeated U.S. Rep. Mark Sanford in his re-election bid last week.
Sanford also expressed his well-wishes to Arrington on Twitter.
Arrington’s Democratic opponent, Joe Cunningham, announced Saturday morning that he's suspending his campaign out of respect for Arrington's recovery.
“As we all know, Katie Arrington is an extremely strong woman and has tremendous faith and an incredibly supportive family," her campaign said on Twitter.