Yvonne Small was injured Friday when someone came up on her from behind in East New York and hit her, the New York Daily News reported. She was treated at Brookdale Hospital but did not require an overnight stay.
No arrest had been made, police said.
Police said at least 10 apparent "knockout" attacks have occurred in the city recently, with reports from elsewhere in the country, including three fatal assaults. Young people supposedly assault strangers with the goal being to make the victim unconscious.
While Small was being attacked, a community activist was holding a rally in East New York against the knockout game.
"We're not going to tolerate anybody striking, hitting or putting their hands on our women in any shape or fashion," Tony Herbert, president of the National Action Network Brooklyn chapter, said.
Putin thinks Obama would save him if he were drowning
Members of Congress to keep receiving porn magazine