The defensive end had practiced all week before experiencing the stiffness and was taken for a CAT scan test. There is no timetable on Kiwanuka's recovery, the team said.
"It's disappointing," said Kiwanuka. "It just feels like a stiff neck. The pain is not intolerable but I want to make sure that I will be OK down the line."
The 1-2 Giants host the 3-0 Bears, the only undefeated team in the National Football Conference, on Sunday night at New Meadowlands Stadium.
(Writing by Larry Fine, Editing by Alastair Himmer)