The Canadian, who aggravated the injury in his 3-6, 6-3, 6-1, 6-3 fourth-round loss to the unseeded Russian, said his knee had been affecting him since his run to the final of the ATP 500 Vienna Open in October last year.
"It's been on and off since Vienna last year...," Shapovalov told reporters.
"I was definitely considering skipping all of clay and most of grass and just coming out for Wimbledon, but it did sound much sweeter, you know, to play Roland Garros and then play the grass.
"That was the decision I made ultimately, and obviously I think I'm still happy I did it, still had a decent result at Roland Garros (reaching the third round) and here. But yeah, it is an issue that I need to fix."
Shapovalov said it would likely take a minimum of two months to treat the injury, adding: "Hopefully no surgery. Obviously with surgery it would be much longer.
"After today it's a little bit difficult. Pretty big setback. Towards the end of the match I couldn't even walk let alone play.
"That's probably the worst that it's been in a long time. I need to talk with the team. I need to try to see some more specialists and see what I can do."
