Officers found the 25-year-old victim down on the platform, "bleeding from a puncture wound to her back," around 1:30 a.m. Thursday, the authority's Joseph Pentangelo said.
She was taken to University Hospital.
Meanwhile, police recovered the knife used and arrested 38-year-old William F. Harden of Brooklyn.
They charged him with aggravated assault, weapons count and possession of marijuana for a joint they said was found in his pocket, Pentangelo said.
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