NORTH Melbourne defender Nathan Grima will miss the start of the season following surgery to a bulging disc in his back.

Grima suffered hip and leg pain on the second day of the club's altitude camp in Utah in November, and took no further part in the training with his teammates.

The pain worsened when he was in his home state of Tasmania over the Christmas break.

Grima sought the advice of an Adelaide-based specialist who determined that the 25-year-old had no choice but to undergo a partial discectomy.

"It had got to the stage where the bit that had broken away from the disc was pressing on some nerves which gave me a lot of pain in my leg and hip," Grima told kangaroos.com.au.

"It's just a lot of wear and tear. David Hall (the surgeon) said sometimes back injuries like this can date back a few years.

"I've had a sore back on and off for a few years but it usually clears up after a couple of days.

"I just presumed that with a bit of treatment I would be right, but a few days turned into a week and a week turned into a month and here we are."

While Grima is expected to spend 12 weeks in rehabilitation, he is confident he can return to full strength.

"Even though I was in pain, I could still smile knowing that in a few months' time I'll be back playing AFL footy," he said.

"People come back from injuries like this who are not full-time footballers and who don't have the medical resources we have ... so I know I'll come back at 100 percent.

"It's relieved the pain ... when I woke up from the surgery I didn't have any pain or tingles in my leg so [it's] so far so good."

Grima finished seventh in North's best and fairest count after a 17-game season in which he emerged as its most important backman.

Having joined the club's rookie list at the end of 2007, he missed the entire 2008 season because of a knee reconstruction.

Grima played 13 games in his 2009 debut season, but faced another injury hurdle when he broke a finger in February 2010.