Knee action shocks are different than lever action shocks. I can't speak to Knee action shocks but lever action units were used on 30's and 40's trucks. In the late 30's and early 40's trucks, single action lever shocks were standard and dual action lever shocks were an accessory. Single action units damped on the rebound after the bump was incurred. The dual would damp on both the up and down strokes. Delco /Lovejoy were the GM units. IIRC Houdaille were the lever action units used by F*rd...Apple hydraulics out of NY are rebuilders of the early shocks and can probably cite chapter and verse on them.
http://www.applehydraulics.com/