A tillage implement for attachment to agricultural soil cultivation machinery. The tillage implement includes a knee having a knee body adapted to be attached to the agricultural machinery. A pivot arm is pivotably attached to the knee body and moves between down and up positions. A tillage blade is rotatably attached to the downward end of the pivot arm and is adapted to roll over and engage the soil being cultivated. A spring is adapted to apply pressure directly to the pivot arm to bias the downward end thereof toward its down position, the knee being adapted to contain and substantially enclose the spring to protect the spring from becoming fouled with foreign matter.