The former Scottish Under 21 cap picked up the injury in the latter stages of the 2-1 win over Luton last month. Up until then Anderson was in sparkling form, chipping in with three goals.
Initial fears were that Anderson had torn his knee cartilage but exploratory surgery proved otherwise.
It is now thought that the ligament was just strained or recieved a minor tear, either way Anderson has no choice but to rest until it is fully healed. The 26-year-old does however expect to be back sooner than later.
"I've been to see the specialist a couple of times and the feeling is that I should be back before too long," he told Mariners Net.
Ando faces wait
"It's a ligament injury, I may have just strained it or even torn it a little, and it was an anxious time when I did it.
"It was right at the end of the Luton game when I did it and I had to come off straight away. It's just one of those things, I'll just have to wait and see if it heals on its own.
"I wouldn't have minded if I had needed an operation, at least I would have known what it was and had a timescale to when I would be back. Now it's just a waiting game to see when it is feeling better."