The 96-year-old monarch has been dogged by problems walking and standing since last year, forcing her to cancel a series of public engagements.
Fears about a flare-up of what royal officials call "episodic mobility problems" have prevented her returning to London to appoint a new prime minister.
The queen had this weekend been expected to attend the Braemar Gathering near her remote Balmoral retreat in northeast Scotland.
A decision on her withdrawal was made for her comfort, British media reported, without quoting sources.
The event, which is always held on the first Saturday in September, is the most famous on the Highland Games circuit.
Senior royals, including the monarch, have attended the games regularly since the mid-19th century, to watch feats of strength and endurance.
Events include tossing the caber, in which kilted competitors endeavour to lift and throw a full-length log Scots pine.
Attendees this year -- the first since 2019 because of the coronavirus pandemic -- include the queen's eldest son and heir, Prince Charles.
She is due to meet Boris Johnson at Balmoral on Tuesday to accept his formal resignation as prime minister.
She will also ask his replacement -- either Foreign Secretary Liz Truss or former finance minister Rishi Sunak -- to form a new government.
Truss and Sunak are vying to become the next Conservative party leader. The winner is due to be announced on Monday.