Knee airbag assemblies

Airbag assemblies are disclosed that include inflatable knee airbags. The knee airbags can include panel(s) forming a main chamber that provides a primary cushioning protection zone to a lower leg of a vehicle occupant. The knee airbags can further include an external chamber panel coupled to a rearward surface of an occupant-facing panel, external to the main inflatable chamber, to form an external chamber facing the occupant. Vent(s) through the occupant-facing panel can communicate inflation gas from the main chamber to the external chamber to fill a space between the vehicle and the lower leg of the occupant, and to control timing of inflation of the external chamber to cause it to inflate on lateral sides of the lower leg of the occupant to thereby limit lateral movement of the lower leg relative to the vehicle.