LONDON -- Princess Anne has been hospitalized after an accident thought to involve a horse left her with a concussion, further straining Britain's royal family as health problems continue to limit public appearances by King Charles III and the Princess of Wales.

The king's 73-year-old sister was admitted to the hospital as a precautionary measure and is expected to make a full recovery after she was injured Sunday while walking at her Gatcombe Park estate in southwestern England, Buckingham Palace said Monday. The cause of Anne's injuries wasn't clear, but doctors said her injuries were consistent with an impact from a horse's head or legs.

"The king has been kept closely informed and joins the whole royal family in sending his fondest love and well-wishes to the princess for a speedy recovery," the palace said in a statement.

The accident is just the latest health scare to hit the House of Windsor in recent months, with both Charles and Prince William's wife, Kate, undergoing treatment for cancer. That has strained the royal family's ability to keep up a full slate of public appearances, with Anne and Queen Camilla taking on more engagements as Charles and Kate took time off to focus on their health.

Anne, in particular, will be missed as she was the hardest working member of the royal family last year.

While she doesn't have the status of Charles or the glamor of William and Kate, Anne is known for her businesslike approach to a busy schedule of public appearances. Anne took part in 457 royal engagements last year, compared with 425 for the king, 172 for William and 123 for Kate, according to statistics compiled by the Daily Telegraph newspaper.

As a result of her injuries, Anne was forced to cancel her appearance at a state dinner in the honor of the emperor of Japan on Tuesday, as well as a trip to Canada planned for later in the week.

"There will definitely be a sort of gap in the royal family lineup for the next few days," royal expert Robert Hardman told the BBC. "But you know, obviously she's got to get well."

Anne has earned her status as a royal family stalwart through decades of work carrying out the awards presentations, ceremonial appearances and building dedications that make up the modern royal whirl.

As president of the British Olympic committee and a member of the International Olympic Committee, Anne was instrumental in helping London win its bid to host the 2012 Summer Olympics and later brought her experience as an Olympic equestrian to the committee that organized the games.

Committee Chair Sebastian Coe praised her stamina, joking at one point that she had usually opened three hospitals by the time she showed up for the average midday board meeting.

"Crucially, she sees the world through the eyes of a competitor," he said at the time.

Anne was herself a member of the British Olympic team in 1976, competing in the three-day equestrian event at the Montreal Games.

She remembers that experience fondly, even though she was thrown from her horse, Goodwill, when it became stuck in boggy mud. Anne remounted and finished the event, but later said she had almost no memory of the day.

"As far as I'm concerned, the lights went out," she later said.

Anne has always been known to speak her mind -- even in extreme situations, such as during a kidnapping attempt in 1974. When the assailant opened her car door and demanded she come with him, Ann demurred.

"I said I didn't think I wanted to go," she told an interviewer. "I was scrupulously polite. I thought, hmph, silly to be too rude at that stage."

Even so, Britain's powerful tabloids sometimes mock Anne's unpretentious and businesslike clothing choices when they notice her at all. She attracts far less attention than many.