The 55-year-old Oscar winner took to the Dolby Theatre stage to present Best Actress alongside Jennifer Lawrence, and the duo addressed Foster's injury onstage when they approached the mic.
"I'm so sorry, what happened to you?" Lawrence asked.
"Streep!" Foster joked. "She I, Tonya'd me." The jab, of course, was a reference to the Oscar-nominated film that dramatized the events of Olympic figure skater Tonya Harding’s life amid the infamous 1994 attack on Nancy Kerrigan.
Lawrence, never one to leave a good joke incomplete, deadpanned: "She tripped me once."
Though Foster and Lawrence, who worked together on 2011's The Beaver, didn't elaborate any further, ET has the real story about what led to her injury. Foster's rep tells ET that she took a fall while skiing, which forced her to use crutches on Oscar night.
Foster and Lawrence presented the Best Actress award on Sunday to Frances McDormand, star of Three Billboards Outside Ebbing, Missouri, breaking from Oscar tradition, which usually calls for the previous year's Best Actor winner to present the category.
Casey Affleck, who won in 2017 for Manchester by the Sea, notified the Academy of Motion Pictures, Arts & Sciences in January that he would not be attending the ceremony, as he did not want to be a distraction from the focus on the performances of the actresses in the category amid controversy over past sexual allegations. The allegations against Affleck, 42, stem from 2010 lawsuits filed by two women who worked with him on his controversial film, I'm Still Here. Affleck has denied the claims and the suits were settled out of court.