The operation will take place next week, the surgeon in currently on holiday and Macca is suffering from cold resulting in a delay.
A mid-March date is now set for Macca's return, by then Town could well need his experience in what looks ever increasingly like a relegation dog fight.
The 34-year-old has promised to return in time for the run-in and help his team-mates.
"I couldn't do anything about it. I couldn't have had the op even if the surgeon was here. I've got a cold as well so that puts it back," McDermott told the Grimsby Telegraph.
"If you go into the op as fit as you can then you get back quicker. It's four to five weeks but sometimes it can be quicker or longer. You can never tell.
"I've had them before and I know what the rehab is all about. I'll be back this season, hopefully.
"I'm disappointed but it got to the stage where it was just unbearable. It was getting more and more frustrating.
"Week-by-week it was getting worse and I tried to miss a few days training but you can't miss too much.
"I had to keep training and by the time I'd finished I could hardly walk. In the last three games I've felt like I was a yard and a half down.
"I had a word with Grovesy and said 'enough's enough', I need it doing.
"I couldn't move around against Wrexham and couldn't push off. It was the twisting I couldn't do and I was getting annoyed with myself.
"The manager totally agreed that it needed sorting. It was affecting my performances and that's the main thing. It's not just me, it's affecting the team and I had to call it a day and he agreed. It has to be done.
"I'm hoping to get back as sharp as I was at the start of the season. Before I got this I felt pretty good and the team put in some decent performances."