“I had bruises around my neck,” she wrote of the time he choked her, “and I was told by him to wear a turtle necks or a scarf to cover them up whenever he would take me out in public. I was frightened to tell anyone about this because of what he may do next. His assistant didn’t even care, and especially the other girls they were in for the money as well.”

In 2008, Mr. Kelly stood trial on child pornography charges in connection with a video that showed him having sex with and urinating on a girl prosecutors said was barely a teenager. She and her immediate family refused to testify, and he was acquitted on all counts. Federal prosecutors have accused Mr. Kelly of bribing the girl’s family to keep them quiet, and a lawyer for that girl — today a woman in her 30s — has said she is now cooperating with federal investigators.

In a chilling echo of those earlier accusations, Ms. Savage said that “Robert always had a fetish” for urinating on women and girls, and that he had done it to her “numerous” times.

There was no indication that the posts were written by someone other than Ms. Savage, but she did not respond to a request for comment to authenticate the material.

Gerald Griggs, a lawyer representing her parents, who have insisted that she was being held in what they’ve described as emotional and sexual captivity , said in an emailed statement on Sunday: “The family is concerned about the allegations made by the social media account purported to be that of Joycelyn Savage. Numerous facts detailed by the account confirm the abuse and coercion that the family has alleged for two and a half years. We are attempting to make contact with Joy and the family is ready to welcome her back with love and open arms.”

In 2017, Ms. Savage recorded a video published on the celebrity news website TMZ in which she said she was fine and “not being brainwashed.” In one of her Patreon posts, Ms. Savage said that she was told what to tell TMZ, and that Mr. Kelly’s assistant “would starve me for days at a time until I learned it right word for word.”