drop sadow??

Hello there I'm trying to render a scene that I have a knife on the kitchen table and I want to have the knife's shadow on the table but I can't see it!! I have the regular shadow and shadow map enabled and I see the shadow in render region but when I render the scene I don't have the Drop shadow!! have shadow's in the scene but I don't have the drop shadow!!(I think that's what it called I'm not sure) I know in photoshop it's called drop shadow.
Any Idea about how I can get the knife's shadow on the table??
Thanks.