MADRID - Spain's King Juan Carlos went into surgery for a hip replacement on Thursday, the latest in a string of operations that have raised questions about the future of his reign.
The 75-year-old monarch waved from the window of the car as he was driven up to Quiron University Hospital in the western suburbs of Madrid, and joked with waiting reporters about the cold weather.
Surgeons were due to fit a permanent prosthesis for his left hip, replacing a temporary implant they put in on September 24.
Thursday's procedure is the king's ninth operation since May 2010. He has had surgery on a benign lump in his lung, his right knee, an Achilles tendon, a slipped disc in his back and five separate hip operations.
The sight of the king appearing in public on crutches and looking frail over recent months and the news of the latest operations had fuelled speculation of a possible abdication, despite palace denials.
Juan Carlos is widely respected for his role in guiding Spain's transition to democracy after the death of longtime dictator General Francisco Franco in 1975.
But his image has since suffered from scandal.
A corruption investigation was opened in 2011 targeting his youngest daughter Cristina's husband, former Olympic handball player Inaki Urdangarin.
Urdangarin has appeared in court but denies any wrongdoing.
Cristina has been linked to Urdangarin's business dealings and she is herself being probed over her fiscal affairs, but she has not been summoned to court and neither she nor her husband have been charged with any crime.
The king also lost sympathy last year for going on an expensive elephant-hunting trip in Botswana, while Spaniards struggled through a recession.
He broke his right hip during the holiday and had to be flown home for surgery, after which he made an unprecedented public apology.
The hunting trip threw the spotlight on the royal family's deluxe lifestyle and on the king's friendship with Corinna zu Sayn-Wittgenstein, a German aristocrat 28 years his junior, who reportedly accompanied him to Botswana.
The king's health has sparked debate about what to do if he is incapacitated and whether he should hand over power to Felipe.
After the operation in September, Prime Minister Mariano Rajoy said the government had no plans to try to regulate the prince's role in case the king is incapable of ruling.
Felipe took his father's place at a national day parade on October 12 for the first time and also replaced him at the annual Iberoamerican summit in Panama last month.
The surgical team on Thursday was led by Miguel Cabanela, a Spanish surgeon based in the United States, from the Mayo Clinic in Minnesota.
Thursday's operation would replace a temporary implant fitted in September, which was coated in antibiotics to kill an infection that had developed in the joint.
Cabanela said the king would need about six weeks to recover and it was hoped he would be walking again in the new year.