The Lionesses captain is confirmed to be missing the rest of the Gunners' campaign and the upcoming Women's World Cup after rupturing her cruciate ligament in Wednesday's Women's Super League clash with Manchester United.
With 15 minutes on the clock, Williamson won possession back from Katie Zelem but immediately fell to the turf in pain, sparking concern from players on both teams.
The 26-year-old was helped to her feet and was able to delicately walk off the Leigh Sports Village field, but it was clear that the England skipper had sustained a serious problem.
Arsenal confirmed on Friday that Williamson had suffered an ACL rupture, which could take at least six and as many as nine months to heal fully, and she will not be present in Australia and New Zealand to help England go for World Cup glory.
Following the Gunners' gut-wrenching announcement, Williamson took to Instagram to admit that she did not have the words to express her feelings, but the Arsenal defender also insisted that she is much more fortunate than other people in the world caught up in more difficult circumstances.
"Until I have the words to express my feelings properly I will struggle to verbalise them. The noise around the situation is loud and I need some quiet to let it all sink in," Williamson wrote.
"Unfortunately the World Cup and Champions League dream is over for me and everyone will think that's the main focus, but it's the day-to-day of what I'm about to go through that is the most draining of my thoughts.
"I had my tears and made my peace with it the night it happened and since then I have been following the steps I'm told to, in order to best help myself in the short and long term.
"Ultimately, I think it's just my time. In the past couple of years alone I have watched teammates beat serious illnesses and adversity with the biggest of smiles on their faces. I also hold perspective that globally there are much greater difficulties and therefore my circumstances right now are just that, circumstantial, and I've seen a lot worse.
"I haven't had a day since last October when I've walked on to the pitch without a physical or mental question mark over me, and that's professional sports, so now I have to listen to my body, give it what it needs and if everything happens for a reason, then we'll see what road this turn sends me down.
"I have given and will continue to give everything that my body, mind and heart possibly has to the Arsenal and Lionesses. I will still be there through thick and thin for all of my teammates and their biggest supporter. I feel your love and support, so thank you! All I ask is for a little bit of time and space to deal with all that is to come."
Williamson is now one of three Arsenal players to be nursing ACL problems, as England striker Beth Mead and Vivianne Miedema remain sidelined with identical injuries, which are proving to be a common occurrence in women's football.
Sarina Wiegman admitted last month that Mead would need a "miracle" to play at the World Cup, and Arsenal have also lost Kim Little to a season-ending hamstring problem.
After Williamson was withdrawn on Wednesday, Arsenal lost 1-0 to Man United to fall six points behind the WSL leaders in third place, while Chelsea are two clear of the Gunners in second with a game in hand.
Jonas Eidevall's side are now preparing for the first leg of their Champions League semi-final with Wolfsburg at the Emirates on Sunday.