Spanish King Juan Carlos will need a second hip surgery in two months after undergoing a temporary replacement on Tuesday, his doctors said after an operation they called "a success".
The 75-year-old king's sixth surgery in two years has revived speculation that the ailing monarch may be close to abdicating, something denied by the palace.
It has also sparked a political debate over whether a law is needed to address a legal vacuum regarding Crown Prince Felipe's executive powers when he stands in for his father, who is head of state.
Juan Carlos helped guide Spain to democracy at the end of the Francisco Franco dictatorship in 1975, but a series of recent scandals has eroded support for the royal family.
Prince Felipe, who has not been tainted by the scandals, represents his father at official events but has no authority to sign decrees and acts into law. The palace has said the king will be able to carry out such duties from the hospital and during his recovery.
Most Spaniards would like Felipe to take over, a poll earlier this year showed, although support for a republic has also grown.
The king, who has been walking with crutches, underwent surgery in a private clinic in Madrid.