Pc Hanif Sanghar even alluded to the fact the arrests were going to be made, telling his 2,700 followers that he was "due to be up very early" yesterday morning.
At 5.06am, just over an hour before a 56-year-old woman and a 28-year-old man were arrested on suspicion of assault, he tweeted to a colleague that he was "on an operation".
Emma Winnall was left with a severed finger, a broken arm and wrist after the attack in her ground-floor flat in Moseley, Birmingham, on May 1.
Police said the arrested woman was not Miss Winnall's daughter Joyce Blencoe, who is also 56.
Chief Insp Sally Seeley, from West Midlands Police, said: "The man and woman arrested in connection with the attack on Emma Winnall are suspects. They are innocent until proven guilty."
She said in Pc Sanghar's keenness to update the public "he used terminology which was wholly inappropriate".
She added: "The officer has been advised and the tweets removed."