An elderly pedestrian was killed yesterday after slipping off his crutches and into the path of a truck on the Upper East Side, cops and witnesses said.

The 65-year-old, whose name was not released, found himself stuck in the middle of East 89th Street near First Avenue as the traffic light turned green at around 8:20 a.m, cops said.

The truck driver waved him on. But when another car began to move north on First, the startled victim fell into the truck’s path, witnesses said.