Portugal's Cristiano Ronaldo walks off the pitch after the 2014 World Cup Group G soccer match between Germany and Portugal at the Fonte Nova arena in Salvador June 16, 2014.
Portugal's Cristiano Ronaldo walks off the pitch after the 2014 World Cup Group G soccer match between Germany and Portugal at the Fonte Nova arena in Salvador June 16, 2014. REUTERS

Portuguese star Cristiano Ronaldo had been nursing thigh and knee injuries in the weeks leading up to the 2014 FIFA World Cup in Brazil. He has since declared himself fit to play and in fact started in Portugal's opening game against Germany which they lost 4-1. Reports now claim that his doctor is warning Ronaldo that playing through his injuries might result in permanent, career-threatening damage.

NBC Sports reports that Portuguese surgeon Jose Carlos Noronha has warned Ronaldo that continuing to play with his existing injuries may lead to a permanent tear in his patellar tendon and risk damaging it beyond repair.

Portugal have lost their Opening match in Group G and will be facing the USA on June 22. The USA won their opening match against Ghana which means that Portugal need to win this match in order to have any hope of advancing to the next round. With defending Champions Spain among the first big teams to book their flights home, Ronaldo will not be keen on missing the upcoming match especially with Real Madrid teammates Fabio Coentrao also out due to injury and Pepe, suspended due to a red card.

Dr Noronha reportedly believes that Ronaldo needs at least two months to fully recover from the injury on his knee. MRI's show that continuing to play has resulted in the tendon concerned being subjected to immense pressure and the risk of further damage.

Ronaldo has been training with the team with his injured knee bandaged up just like he did prior to the opening match. He has sent out a video after their loss to Germany assuring fans that he and the team are ready and confident for the next match and that they can still look forward to a great World Cup for Portugal.

Watch Cristiano Ronaldo's message to Portugal fans

Portuguese goalkeeper Beto has also backed up Ronaldo and said in a report on football website Soccerly that the Ballon d'Or winner is 100% fit to play against the USA. He also denied rumours that the national team captain had left earlier than his teammates.

"Cristiano is 100 percent fit to play. Every match he starts to play, it's because he's fit to play, He loves football but his body is the most important thing for him, to be fit, to be healthy so if he starts the match it's because he's ready, he's fit." said Beto.