But the Crown Prince said on Thursday that he expected his stint as regent to be short-lived, with the King soon back on his feet.
“I think he's going to be on the mend extremely quickly,” Haakon told Norways NTB newswires from Estonia, where he is currently on an official visit with Crown Princess Mette-Marit.
“The king is extremely good at thinking that he is healthy,” he added. “Right now, I think his foot needs some rest, and then it will get better. Then he will be back,” he said.
The Royal Court announced on Wednesday that the King was temporarily stepping down from his duties due to a worsening of a problem with one of his feet, which meant he could no longer walk.
The King, 80, was admitted to hospital in November to treat an infection, but was released after just three days. He underwent surgery for bladder cancer 14 years ago and had another operation in 2005 on a cardiac valve.
Despite his age, the King is still highly active and on the calendar of the Royal Court's website, he is expected to engage in seven official meetings next week, including one with Sir Chief Marshal Sir Stuart Peach, the UK's Chief of Defence Staff and Chairman of the Nato military committee.