The discolouration on her left hand was originally spotted as she posed alongside her daughter, Princess Anne, with Queen Rania of Jordan and King Abdullah II of Jordan and their son, The Crown Prince, at Buckingham Palace last week.
Fans quickly took to social media to voice concerns.
One fan commented: “I love keeping up with Queen Elizabeth II but I’m concerned”
“Why does she have such a terrible bruise on her left hand. Did I miss something? But as always, she looks stunning!” read another.
Another comment read: “Look at Queen Elizabeth’s hands. They look red and bruised. Like someone was trying to find an artery.”
Earlier on Clarence House tweeted images of a young Prince Charles and his mother to kick off celebrations.
“This photo shows The Queen and His Royal Highness when HRH was formally invested with the title of The Prince of Wales 50 years ago,” read the photos caption.
The event also marks the first time Kate and a pregnant Meghan have made a joint appearance since Christmas, amidst rumours of a royal rift.