A father's "brutal" regime resulted in his daughter becoming an "elective mute" and her sister developing a "fixed smile", the High Court heard.
A judge was told the girls' behaviour was a response to "frightening, sadistic and violent" experiences.
The court heard their father sexually abused them, slapped, punched and kicked them, pulled their hair, made them get up early and ordered them to bed as soon as they arrived home from school.
The abuse was revealed after social services asked the judge to make orders to protect them from their father.
Mrs Justice Knowles analysed the case at a private family court hearing in London on Friday.
She said the girls were now in foster homes and their father was serving a 22-year prison term after he was convicted of a string of offences.
She ruled the girls' father should have virtually no involvement in their lives.
Council officials were told they did not need to consult or inform the father about "any aspect" of the girls' "progress, development or well-being" but he could be informed of any life-threatening medical emergency.
The judge said the girls and the council involved cannot be identified.
The father was found guilty of cruelty and a number of child sex offences after a trial, while the girls' mother had been convicted of neglect and given a suspended prison sentence.
Mrs Justice Knowles said: "Both girls experienced significant physical, sexual and emotional harm in the care of their parents.
"Both girls have recounted frightening, sadistic and violent experiences and both developed a variety of behaviours to manage their experiences.
"They were hyper-vigilant and remain so."
More from UK
One of the girls had become an "elective mute" and the other "developed a fixed smile", the judge said.
She added: "Both girls have expressed great fear/terror of their father and both have required much reassurance that he remains in prison, does not know where they are, and would not come out of prison until they were adults."
[contf] [contfnew] 
Sky News
[contfnewc] [contfnewc]
