King Juan Carlos of Spain was taken to hospital on Friday night for hip surgery to give him greater mobility.
The operation is on his left hip; he has already had two operations to his other hip this year after a safari accident in Botswana.
He spoke about the imminent hospital trip a week ago.
“As you’ve observed, I have some mechanical problems which have reappeared these past few days and which will oblige me, following medical advice, to interrupt my official schedule to go to the workshop,” Juan Carlos said.
The 74-year-old monarch put off the operation in order to attend a recent Spanish-Latin American summit.
Juan Carlos has had several health problems over the past couple of years. In 2010, he had surgery over a benign lung tumour. Last year he received an artificial knee and had treatment for a damaged tendon.