Queen Elizabeth II will undergo an operation to remove torn cartilage in her left knee this week, Buckingham Palace has announced.
Friday's procedure will mark the second time this year the British monarch has undergone treatment for a knee problem. In January, she took a two-week break after similar surgery on her right leg.
This week has seen health issues arise in a number of royal families around the world, with Norway's King Harald and Japan's Crown Princess Masako both being checked into hospital.
The Norwegian monarch is recovering from bladder cancer surgery in an Oslo hospital. Doctors say King Harald is "in good shape" after having his bladder removed and replaced with an artificial organ during a five-and-a-half hour operation on Monday.
"The operation went completely according to plan," said surgeon Trygve Talseth. Another member of the medical team attending the 66-year-old monarch said: "We haven't found anything that would indicate the king won't recover completely." King Harald is expected to remain in hospital for two to three weeks.
Meanwhile, Crown Princess Masako is back at home, having been discharged from a Tokyo hospital after being briefly treated for shingles. The princess, who turned 40 on Tuesday, is continuing her recovery from the painful virus at home.