The Brazil midfielder suffered a knee injury in April which prematurely ended his season.
He is now back and featured in the opening preseason win against Carlisle United.
"I feel good now," he told newcastleunited.com. "I've had a long time to recover. The start of it was very difficult as, personally, I was very frustrated about the injury at the end of the season.
"There was a lot of important games and I could have been with the team. I was very sad but I knew I had to step out and recover because of my knee as I couldn't help the team in the way I wanted. It was the best decision and I had enough time to recover and come back, starting with the guys in pre-season.
"My knee is good, I feel fully fit and happy. Injuries are not what you want but they can happen in football sometimes and you just have to deal with them and do everything you can to be fit. I now hope to have a season without injuries."
Happy Elanga now a teammate
Joelinton also welcomed new teammate Anthony Elanga, after his signing from Nottingham Forest.
The Brazil midfielder added, "He's a really good player with a lot of qualities. He's very fast, can score or assist and has been tough to play against so I'm happy he's now joined us!
"He will be very welcomed into the group and we will do everything to make sure he feels at home and comfortable so he can do what he has been doing for Nottingham Forest. I'm very happy he has signed and I wish him all the best."