US Supreme Court judge Ruth Bader Ginsburg has fractured three ribs in a fall on Wednesday, the court says.
The fall happened in her office at the Supreme Court in Washington.
Ms Ginsburg, 85, went home but was in discomfort and went to George Washington University hospital on Thursday morning, a statement said.
Tests showed that she had fractured three ribs on her left side and she has been admitted for observation and treatment.
It meant that Ms Ginsburg - the most senior justice on the court's liberal wing - was not present for Thursday's investiture of Brett Kavanaugh, whose appointment led to protests following allegations of sexual misconduct.
The appointment, confirmed last month by the Senate, restores the nine-member court's conservative majority. The court has the final say on issues such as abortion, gun control and voting rules.
President Donald Trump, who nominated Mr Kavanaugh and described the claims against him as a "hoax", attended his investiture.
On Twitter, many were quick to offer the liberal justice assistance in the form of extra ribs and human shields to ensure she made it through the Trump presidency.
Okay listen up! I'mma start a national sign up sheet for people to volunteer to literally physically carry #RuthBaderGinsburg around everywhere she wants to go and cut her food for her and become human shields for her for the next 2.5 years. Who's in? #RBG #Breyer too— Clay Aiken (@clayaiken) November 8, 2018
Ruth Bader Ginsberg can have my ribs. And my kidneys and a lung. And anything else she needs. She can even have my husband on Thursdays.— Alyssa Milano (@Alyssa_Milano) November 8, 2018
Prospect of head-spinning change
By Anthony Zurcher, BBC North America Reporter
Many on the left have quipped that Ms Ginsburg, the liberal lioness of the Supreme Court, should be encased in bubble-wrap to ensure she remains safe and healthy until the end of Donald Trump's term. The next time they say that, they may not be joking.
The justice's recent fall has once again sparked concerns for her health and worries about the prospect that the Supreme Court could tilt even further to the right.
When Mr Trump replaced the ultra-conservative Antonin Scalia with Neil Gorsuch, there was no ideological change. But swapping right-leaning moderate Anthony Kennedy with Brett Kavanaugh shifted the court to the right in varying degrees based on the issue.
If the president has the opportunity to fill Ms Ginsburg's seat because she resigns or dies, the change would be a nightmare scenario for Democrats.
Just two days after the mid-term elections, the significance of Republicans maintaining control of the Senate - which confirms presidential nominees - has been put in stark relief. For many conservative voters, another opportunity to shape the Supreme Court was a big part of what the mid-term election fight was all about.
Who is the 'Notorious RBG'?
Ms Ginsburg was appointed to the Supreme Court in 1993 by President Bill Clinton. She had previously focused her work on women's rights and started the first law journal dedicated to the topic.
Ms Ginsburg has survived cancer and in 2012 cracked two ribs in a fall at her home.
Some of her legal opinions, coupled with her refusal to step down during the Obama era, have seen her gain popularity in some quarters and earned her the nickname Notorious RBG.
She is the subject of both a recent documentary, RBG, and a forthcoming feature film, On the Basis of Sex, in which she is played by actress Felicity Jones. The feature film is about a landmark Supreme Court case in which Ms Ginsburg argued for fathers' rights and against gender discrimination.