Pope Francis has urged elderly people to consider their advanced aging a blessing, not a condemnation, as he himself struggles to cope with a bad knee that has made walking nearly impossible.

The 85-year-old included himself among the people addressed in his second message ahead of the World Day for Grandparents and the Elderly, which was released on Tuesday.

He instituted the day, celebrated at the end of July, to drive home his belief that old people must be considered a resource for younger generations, not part of today’s “throwaway culture”.

In the message, Francis noted that old age is a time of life that is not understood even “by those of us who are already experiencing it”.

“Even though it eventually comes with the passage of time, no one prepares us for old age, and at times it seems to take us by surprise,” he wrote.

But he urged his fellow elderly people to embrace their advanced ages as a gift of a long life, and not lament the diminishment of their strengths or sense of usefulness.

“Along with old age and white hairs, God continues to give us the gift of life and to keep us from being overcome by evil,” he said.

“Ageing is not a condemnation, but a blessing!”

Francis has had strained ligaments in his right knee for several months, and recently said he can no longer walk and must rest on doctors’ orders.

He was seen in public last week for the first time using a wheelchair, raising questions about his ability to negotiate a trip in early July to Congo and South Sudan.

This week, the Lebanese government confirmed a planned visit next month had been postponed because of Francis’s health.

The Pope closed the message noting that war has returned to Europe just as the generation that experienced the last war on the continent is dying out.

He prayed that all elderly people are made into “artisans of the revolution of tenderness, so that together we can set the world free from the spectre of loneliness and the demon of war”.