The man, Ramakrishnan, a relative of the 17-year-old girl, used to take her to hospital for treatment, they said.
Ramakrishnan took her to the hospital at Pollachi on November 8, but did not return even the next day and there was no word from him besides his mobile phone was also switched off, they said.
Based on a missing girl complaint filed by the girl's parents, police found Ramakrishnan hiding in a village.
On the basis of interrogation, it came to the fore that the accused had held the girl captive in a house at Eripadi village and allegedly sexually assaulted her, police said.
After rescuing the girl, police arrested Ramakrishnan on charges of abduction and rape, they added.