Pope Francis’s trip to Africa next month has been cancelled because of the 85-year-old pontiff’s knee ailment, the Vatican said on Friday, raising questions about his ability to walk during the rest of his papacy.

The decision to scrap the July 2-7 trip to Democratic Republic of Congo and South Sudan was taken “with regret” at request of the pope’s doctors, who have been treating him for a torn ligament in his knee.

He has been using a wheelchair for the last month, although he has kept up his activity, including a meeting on Friday with European Commission president Ursula von der Leyen.

Vatican spokesman Matteo Bruni said the pope, who was elected in 2013, would skip the trip “in order not to jeopardise the results of the therapy that he is undergoing for his knee” and that it would take place at “a later date to be determined”. Vatican sources have said the pope has been receiving several injections a week for the ailment, as well as physical therapy.

The surprise announcement came just two days after the Vatican released the names of journalists whose requests to accompany the pope on the papal plane had been accepted and preparations in both countries were well under way.