Madrid, Cristiano Ronaldo has vowed he'll come back much stronger from the left knee injury he suffered in Portugal's Euro 2016 final defeat of France.

Ronaldo suffered the injury following a crunching tackle from Dimitri Payet, with reports claiming the 31-year-old could miss Madrid's start to the LaLiga season.

"Hi everyone! I just wanted to thank all my fans," Ronaldo said in a video on his Instagram account.

"I wanted to tell them that all is well and that I will come back much stronger. Thank you, long live Portugal!"

After limping off the field, the three-time Ballon d'Or winner tried to continue playing but he was unsuccessful, though Portugal still managed to go on and win thanks to substitute Eder's 109th-minute strike.