The midfielder is eager to start training.
“It’s been tough, a lot of time in the gym and a lot of time in the physio room and not playing football, something I’m not used to,” he said.
“I’ve never had an injury like that before. I’m still young, but it’s the first injury I’ve had so I couldn’t really enjoy not playing.
“I definitely am look forward to getting my boots back on and kicking a ball around again and getting back on the pitch and obviously in the Premier League, which is a big step up.
“So it’s a really exciting time in my career.”
Butterfield, who has represented England Under-21s, has played twice at Carrow Road for his former club.
He said: “I’ve played here a couple of times for Barnsley and there was always a fantastic atmosphere.
“The pitch is lovely and we’ll be looking to play some good football here. I’m just delighted to have it sorted and looking forward to getting into it.”