The 29-year-old Ballon d’Or winner has laboured with a knee and thigh problem recently, but took a full part in Sunday’s final training session in Salvador.
“I have been practising for a few days, which I couldn’t do if I was injured,” said superstar Ronaldo ahead of the Group G clash.
“I’d like to be 110 percent, but I am at 100 percent and ready to help the national team.
“Obviously, I would like to play without pain, but in my entire career I have always had injuries and knocks to deal with, but I am ready to play.”
Ronaldo was dismissive of media reports which implied he would not be fit for the Germany clash.
“The press say whatever they want, I have been playing at a high level for years and I am used to those unhappy statements,” he said.
“The media often just throw things up in the air and try to hit something.
“The most important thing is the health of the player and if there is any problem during the game, I will tell my coach.
“I am not willing to risk my career on one game, if I am not fit, I won’t play.”
The Arena Fonte Nova clash is a re-run of Portugal’s Euro 2012 opener against Germany, when they lost 1-0, while the Germans have beaten the Portuguese at three of the last four major tournaments.
“Obviously the historical record has been positive for Germany recently, but I remember a recent case when Real Madrid couldn’t beat Bayern Munich and that changed,” said Ronaldo, whose Real beat Bayern in this season’s Champions League semi-final.
“I hope this is the year Portugal change things against Germany and maybe tomorrow is when that will happen.”
With 111 appearances for his country, Portugal’s all-time record scorer with 49 goals, Ronaldo will be playing at his third World Cup.
Having been part of the side which lost the third-place play-off to Germany in 2006 and was beaten by Spain in the round of 16 four years ago, Ronaldo insists he has nothing to prove at a World Cup.
“I don’t think I have to show anyone anything. If you look at my statistics and resume you’ll see that,” he said brusquely when asked if his World Cup record was the only blot on his stunning CV.
“I have no words for that question, I just have to continue my career, which has been great so far.
“We have to be realistic (at the World Cup), we aren’t favourites and, in theory, there are teams stronger than ours.
“We must be humble and accept this will be a difficult tournament, but we will face one of the favourites and we have the chance to try and win.”
Portugal coach Paulo Bento said it is impossible to underestimate Ronaldo’s importance to his side’s hopes of a first World Cup title.
“The importance of having someone like Cris is enormous, because he influences the way we play and his team-mates know that,” said the 44-year-old.
“His projection is global. He’s huge, not just in our country.
“The pressure we put on ourselves is not enough, we have to get through the group and take it from there.
“But having the best player in the world doesn’t necessarily mean we will automatically be world champions.”