The 23-year-old from Cairo left the court in agony after losing one game which was so painful it suggested he might have been better never to have taken the court.
It was won 11-2 by Aamir Atlas Khan, the Pakistan number one, and Ashour's retirement cost the tournament someone who was simultaneously its most charismatic player, the unofficial favourite for the title, and a local hero with strong connections to the city.
"I'm very sad. I don't know what to say. It means so much to me," Ashour said, close to tears. "I felt it first in training back in Egypt a week ago.
"I was going to hospital every day and I hoped it would be all right when I got here. There was no way I was going to miss the World Open.
"I really wanted to play and stay world number one. But when I was here I felt it go again.
"I somehow managed to get through my first match (against Kristian Frost of Denmark) and I thought that with a rest day, if I prepared carefully, I might get through another one. It was no good - I just couldn't move."
Ashour is sponsored by ATCO, whose vice-chairman Ziad Al Turki is responsible for bringing a world championship to Saudi Arabia for the first time.
It was in this same arena a year ago that Ashour won a thrilling final in the Saudi International against England's Nick Matthew to snatch the year-end world number one spot.
Matthew, the top seed, could now become the main beneficiary of Ashour's ill fortune, and has a last 16 encounter with Hisham Ashour, Ramy's elder brother, on Monday.
Others who may take advantage are Ashour's compatriot Amr Shabana, the 31-year-old defending champion, who plays Azlan Iskandar of Malaysia, and a third Egyptian, Karim Darwish, the former world number one.
Darwish progressed safely to the third round with a 11-8, 11-9, 11-5 win over Tom Richards of England.
Another front runner to impress was James Willstrop, the world number five from England, whose 11-6, 11-3, 11-3 win over Borja Golan of Spain appears to have opened up a route through to the semi-finals in place of Ashour.