President-elect Joseph R. Biden Jr. twisted his ankle playing with one of his dogs over the holiday weekend, an injury that his doctor said on Sunday resulted in hairline fractures in his foot that would most likely require him to wear a walking boot for several weeks.

Although initial X-rays showed no obvious fracture, a “follow-up CT scan confirmed hairline (small) fractures of President-elect Biden’s lateral and intermediate cuneiform bones, which are in the midfoot,” Dr. Kevin O’Connor, the director of executive medicine at GW Medical Faculty Associates, said in a statement distributed by Mr. Biden’s office.

Mr. Biden visited an orthopedic specialist in Newark, Del., on Sunday afternoon for just over two hours, leaving just before 6:30 p.m. and going to an imaging center for a short time for the additional CT. A Biden spokesman said the president-elect had scheduled the follow-up on Sunday to avoid disrupting his schedule on Monday. A van was maneuvered to block reporters and photographers from seeing Mr. Biden as he entered the doctor’s office.

Mr. Biden, 78, is already operating on a crunched transition time frame, after the head of the General Services Administration did not formally acknowledge the presidential election results for weeks after Election Day, temporarily depriving Mr. Biden of access to federal resources and preventing his advisers from beginning coordination with Trump administration officials.

President Trump, who has refused to concede to Mr. Biden, reposted on Twitter an NBC News video of Mr. Biden leaving the doctor’s office on Sunday, and added, “Get well soon!”

Mr. Biden slipped and injured himself Saturday while playing with Major, a German shepherd the Bidens had fostered that they then adopted in 2018. They have another German shepherd, Champ, and have announced plans to get a cat when they move into the White House next year, as well.