U.S. Supreme Court Justice Ruth Bader Ginsburg is already up and working in her hospital room, a day after breaking three ribs in a fall, her nephew said late on Thursday at the Hollywood premiere of a film about her life.

Ginsburg, a ground-breaking liberal jurist who at 85 is the oldest U.S. Supreme Court justice, was hospitalized on Thursday after falling at her office at the court, a court spokeswoman said.

"The last I heard she was up and working, of course, because what else would she be doing, and cracking jokes," her nephew Daniel Stiepleman said at the premiere of the film "On the Basis of Sex", about a gender-based discrimination case Ginsburg tried as a young lawyer in 1972.

"I can't promise they were good jokes but they were jokes," said Stiepleman, who wrote the script for the film with input from the justice herself.

Ginsburg, who made her name as an advocate for women's rights, is one of four liberals sitting on the court, to which she was appointed in 1993 by then President Bill Clinton.

The court's 5-4 conservative majority was restored last month when the Senate confirmed Republican President Donald Trump's appointee Brett Kavanaugh after a contentious nomination process in which Kavanaugh denied a sexual assault allegation from his youth.

Ginsburg went home after the fall but experienced discomfort overnight and went to George Washington University Hospital on Thursday morning, court spokeswoman Kathy Arberg said in a statement.

Tests showed Ginsburg fractured three ribs on her left side and she was admitted for observation and treatment, Arberg added. The court is due to hear its next arguments on Nov. 26.

If Ginsburg were unable to continue serving, Trump could replace her with a conservative, further shifting the court to the right. A potentially dominant 6-3 conservative majority would have major consequences for issues including abortion, the death penalty, voting rights, gay rights and religious liberty.

As the oldest justice, Ginsburg is closely watched for any signs of deteriorating health. She has bounced back from previous medical issues and has fallen twice before at her home, in 2012 and 2013, leading to rib injuries. She was treated in 1999 for colon cancer and again in 2009 for pancreatic cancer, but did not miss any argument sessions either time.

In 2014, doctors placed a stent in her right coronary artery to improve blood flow after she reported discomfort following routine exercise. She was released from a hospital the next day.

Trump went to the court on Thursday for a ceremony welcoming Kavanaugh to the nation's highest court. Kavanaugh was sworn in to the lifetime job last month. The president sat with first lady Melania Trump at the front of the marble-walled courtroom near the justices' mahogany bench, making no public remarks.

Some leading congressional Republicans, including Senate Majority Leader Mitch McConnell and outspoken Trump ally Senator Lindsey Graham, attended. The event came a day after Trump fired Jeff Sessions as attorney general; Matthew Whitaker, who Trump named as Sessions' interim replacement, participated.

Critical comments

Ginsburg called Trump an egotistical "faker" when he was running for president in 2016, in an unusual foray into politics by a justice. Trump responded, saying her "mind is shot" and she should resign. Ginsburg later expressed regret, saying "judges should avoid commenting on a candidate for public office."

She is a hero among many U.S. liberals, who revere her as "The Notorious R.B.G", a nickname based on a late rap star. A documentary film about her, "RBG," was released earlier this year, and the Hollywood biopic will be released on Christmas.

The director, Mimi Leder, called described the film as Ginsburg's "origin story", a term used in superhero movies.

"Our thoughts are with her tonight after her fall yesterday. We send her our love and pray for a speedy recovery. I have it on good word that shes in great shape, and she is shooing the doctors out of her room so she can work," Leder said at the premiere. She told Reuters her own information about Ginsburg's health had come from Stiepleman.

Ginsburg has helped buttress equality rights during her time on the high court, including in sex discrimination cases.

Her career was shaped in part by discrimination she faced as a young lawyer in a predominantly male profession: she was one of just nine women at Harvard Law School in the 1950s, and later struggled to find a firm that would hire her.

"She was making mistakes, finding out who she was, had a very young family, her husband wasn't very well," actress Felicity Jones, who plays her in the film, told Reuters on the red carpet. "She was juggling a lot of difficult things at the same time but always (had) this absolute commitment to the law."

Ginsburg voiced support for the #MeToo movement against sexual misconduct after Kavanaugh was accused of sexual assault by a university professor, saying that unlike in her youth, "women nowadays are not silent about bad behavior."

Kavanaugh's Senate confirmation process convulsed the nation just weeks before Tuesday's congressional elections in which Trump's fellow Republicans lost control of the House of Representatives but expanded their majority in Senate.

On Wednesday, Trump credited the fight over confirming Kavanaugh, who was strongly opposed by Democrats, for the gains in the Senate.