The prolific Portuguese set alarm bells ringing on Tuesday when he ended training prematurely with a knock but was fit to train again the following day.
Although Ronaldo scored the final goal in Real's 4-1 extra-time win over Atletico in the 2014 final in Lisbon, he has admitted he was far from at his best due to a hamstring problem and is determined to put in a better performance at Milan's San Siro on Saturday.
"Cristiano always appears in the games that matter. I'll be at 100 per cent. On Saturday, I'll be in better form than I was in Lisbon," Ronaldo told Spanish television channel La Sexta.
"In Lisbon, my hamstring was hurting me. It was pretty bad. It was terrible because you know that in certain moments you could give more but you can't because your body doesn't respond."
Ronaldo has scored -- and been on the winning side -- in both the Champions League finals he has played in, having also won in 2008 with Manchester United.
He is top scorer in this season's tournament with 16 goals and is one strike away from equalling the record tally of 17 he set in 2013/14.
Real's all-time top scorer also gave the club a lift before the final by declaring he wants to stay at Real for the long term.
"Real Madrid would be making a smart decision if they offered me a new contract," he added.
Zinedine Zidane's men are without defenders Raphael Varane and Alvaro Arbeloa for the game, while Atletico have a clean bill of health.
It's a far cry from the dishevelled state in which Diego Simeone's team arrived at the 2014 final, when they struggled with fitness after a long season and suffered key injuries.
On their way to that Madrid showdown Atletico won 1-0 at the San Siro. Real, on the other hand, have never won a competitive game at the stadium in 13 attempts.
Defender Diego Godin says Atletico are in better shape than last time around, and thinks his side's team ethic, instilled into them by the charismatic Simeone, could prove key to winning their first European Cup.
Godin told Uefa.com: "Our big secret is the effort the team puts in. The way the whole team works to help the defence is incredible.
"The forwards - Fernando Torres, Antoine Griezmann or Yannick Carrasco - are always with us, defending in our box.
"That shows how committed we are as a team, and how much we believe in our style of play."
