Real coach Carlo Ancelotti rested the Champions League top scorer for Saturday's 4-0 La Liga win at Real Sociedad that helped them keep pace with leaders Atletico Madrid and second-placed champions Barcelona. (Agencies)
The Portugal captain, who has a record-equalling 14 goals this season in Europe's elite club competition, has complained of discomfort in his left knee but Ancelotti said he should be available for the second leg in Germany after a few days' rest and treatment.
Ronaldo made his 100th Champions League appearance in the first leg at the Bernabeu and his goal matched Lionel Messi's single-season record set in 2011/12.
Ronaldo's overall tally in the Champions League is 64 goals, three behind Barcelona's Messi, and he has 54 in his last 44 outings for Real and Portugal, including five hat-tricks.
Real have a slight doubt over the fitness of record signing Gareth Bale after he sustained a small gash to his right knee in Saturday's win in San Sebastian.
The Wales winger, who scored with a brilliant long-range strike to make it 2-0, needed a couple of stitches in the wound, local media reported.
Ancelotti did not sound too concerned at his post-match press conference.
"This victory strengthens us and we also avoided injuries and were good physically," the Italian said. "We played very well, intelligently. We started at a very high pace and had more intensity in the second half.
"Everyone had a good game and I'm pleased because it wasn't easy. I'm very proud to manage this team. I have players who like to fight and we're going to fight until the last match."
It is this fighting spirit this season that has turned things around between the Germans and the Spaniards after Dortmund ousted Real at the semi-final stage last season.
Dortmund, however, boosted their own confidence with a 2-1 comeback win over VfL Wolfsburg on Saturday that tightened their hold on second place in the Bunsdesliga and took pressure off the team as they chase an automatic Champions League spot for next season.
"This win was very good for us," said Dortmund coach Juergen Klopp. "Had we lost we would have had to surrender to the murderous pressure. It was important to win and go into Tuesday's game with a good feeling.
"We will not give anything away for free. We want to have two good halves on Tuesday and then we can see what comes out of it."
Klopp will have top scorer Robert Lewandowski back for the game after the Poland international sat out the first leg with a suspension.
Lewandowski was on target in the win over Wolfsburg and his fire power will be crucial on Tuesday if the Germans are to have any chance of progressing.
Dortmund came from a goal behind and scored twice in the second half to win against Wolfsburg with Marco Reus, who scored the winner, saying a performance like that against Real was what was needed.
"We are a long way from surrendering this tie," Reus said. "If we play like we did in the first half then it will be difficult," said the Germany international.
"If we play like we did in the second half then it could work. It is incredibly difficult but we will give it all we've got. In football anything can happen," Reus told reporters.
Real coach Carlo Ancelotti rested the Champions League top scorer for Saturday's 4-0 La Liga win at Real Sociedad that helped them keep pace with leaders Atletico Madrid and second-placed champions Barcelona.