Walker fell awkwardly towards the end of the play-off final victory against Preston and had to be carried off.
He said to the official site, “I’m having an operation on the knee next week. It’s a cruciate operation, but it’s only one and I’m hopeful that it will go well.
“After that it will just be a case of going through the rehabilitation and waiting for the knee to heel. It’s difficult to put a timescale on it, we’ll just have to wait and see after the operation.
“I’m hopeful that it won’t be too long, though.”