A police commando unit raided the home in the town of Haßmersheim in Baden-Württemberg on Wednesday and detained the father, mother and son on suspicion of imprisoning the woman and brutally forcing her to perform household tasks.
In an least one instance, the father allegedly raped the victim. A source close to the investigation said the son was a minor.
"During the entire time, the victim was repeatedly abused, humiliated and threatened," prosecutors in the city of Mosbach said in a statement.
The family "is strongly suspected of using violence and threats to force the victim to perform household chores and to snuff out any hope of fleeing from her thoughts."
Prosecutor Franz-Josef Heering declined to elaborate on the case but told news agency AFP the alleged victim and the family members were all German citizens and knew each other before she was believed to have been taken prisoner.
He declined to comment on the ages of the suspects.
Authorities said at least one member of the family kept watch over the woman at all times but that she was nevertheless able to escape last weekend through an open window.
Heering said she reported her alleged ordeal to police in a neighbouring town.
Because they had reason to believe the family held weapons, police dispatched the commando unit.