Ronaldo has been struggling with a knee problem throughout the World Cup so far but has completed 90 minutes in both his side's group games to date.
|WORLD CUP SOCIAL HUB
|Keep up with all the latest news from Brazil and get involved in the debate on Twitter with our new World Cup Social Hub|
"He is better than when he arrived in the national team set-up," the Portugal team doctor told Publico.
"In medical terms I do not know if he is 100 per cent, but is clinically he is well and is able to compete. He has a little discomfort because of the tendinitis he suffered, but the rest is fine."
Paulo Bento's side have struggled with injuries since arriving at the World Cup, with left-back Fabio Coentrao ruled out of the tournament after the 4-0 defeat to Germany with a thigh problem and Rui Patricio and Hugo Almeida also suffering fitness scares.
According to Jones, these problems were to be expected due to Portuguese players experiencing a high number of fitness issues over the season and the difficulty of recovery in the Brazilian heat.
"Two-thirds of our players have had a very full season of injuries," Jones explained.
"We had tests that ensured they were fit but we have 12 athletes with muscle injuries during the season and we always had to be on top of the medical departments of the clubs.
"The weather should not scare anyone. The weather conditions are not so severe as to limit the consistency of the players. There is a performance problem, but a problem of the recovery effort, which will be greater."
Portugal face Ghana in their final group-stage game on Thursday, needing a win to stand a chance of progressing.