Pope Francis has named a Vatican nurse who he said had "saved my life" to become his personal healthcare assistant, a new role for his papacy.

The appointment comes as the 85-year-old pope suffers from knee pain that has forced him to cancel numerous events.

He also admitted last week after a trip to Canada that he must slow down or even start thinking about retiring.

"The Holy Father has nominated Massimiliano Strappetti, nurse coordinator of the Directorate of Health and Hygiene, as his personal healthcare assistant," the Vatican said in a short statement.

Mr Strappetti was widely identified as the Vatican hospital nurse hailed by the pope in an interview last year for persuading him to undergo surgery for an inflammation in the intestine.

"He saved my life!" the pope told Spanish radio Cope following his July 4 surgery.

He added that the nurse had been there for three decades and was a "man with a lot of experience".