Masked bicyclist stabs pedestrian on sidewalk on Upper East Side

A masked bicyclist leaped off his bike and stabbed a pedestrian as he walked along a sidewalk on the Upper East Side on Thursday afternoon, police said.

The victim was walking on 63rd St. at Third Ave. just after 1:50 p.m. when the attacker, who was dressed all in black and wore a black mask, pounced on him, cops said.

The cyclist stabbed the man in the back and arm, then fled.

Medics took the victim to New York-Presbyterian Hospital Weill Cornell with injuries that weren’t believed to be life-threatening.