Kennedy had been accused of twisting a nurse's arm and kicking another in January as he tried to leave the maternity ward of a suburban New York City hospital with his newborn son.
His attorneys had argued that Kennedy wanted to take his child out for some "fresh air" and that the staff had overreacted.
But one of the nurses, Cari Luciano, testified that as Kennedy tried to get past the nurses and into the stairwell, his infant's head was being jostled, unsupported, in his arms. She said that she instinctively reached out to steady it when Kennedy kicked her squarely in the pelvis.
Nurse Marian Williams said she saw Kennedy kick Luciano with "such force" that it knocked her off her feet.
Kennedy is the youngest son of the former U.S. attorney general and U.S. senator, who was the younger brother of slain President John F. Kennedy.