 Get your hand off my knee. 
( ( ( Get ( your hand ) ) ( off ( my knee ) ) ) . )
(ROOT (S (VP (VB Get) (NP (PRP$ your) (NN hand)) (PP (IN off) (NP (PRP$ my) (NN knee)))) (. .)))
You can keep your hand on my knee.
( You ( ( can ( ( keep ( your hand ) ) ( on ( my knee ) ) ) ) . ) )
(ROOT (S (NP (PRP You)) (VP (MD can) (VP (VB keep) (NP (PRP$ your) (NN hand)) (PP (IN on) (NP (PRP$ my) (NN knee))))) (. .)))