According to The Daily Telegraph, Camilla suffered the injury prior to the Queen’s death and has been in “quite a lot of pain” as she carries out duties alongside the King.
A source told the newspaper she has just been “getting on” with the job of supporting the King during an emotionally and physically gruelling week.
“It is unfortunate timing to say the least but she’s been an absolute trouper,” the source reportedly told the newspaper.
The King’s spokesman told the PA news agency that they “won’t comment on medical conditions” when asked for a comment on the Queen Consort’s condition.
Details of how public can visit Queen lying in state
King to visit Wales on Friday
It comes as the royal couple are due to visit Wales on Friday – the King’s first visit since he ascended to the throne.
The King and Camilla will attend a service of prayer and reflection at Llandaff Cathedral before receiving condolences at the Welsh parliament, the Senedd.
He will later hold a private audience with Welsh First Minister Mark Drakeford and the presiding officer at Cardiff Castle, although a protest against the monarchy is expected outside.
Charles will then attend a reception hosted by the Welsh Government, before returning to Buckingham Palace in the evening to host faith leaders in the Bow Room.