Physics Asset: edit constraint

I have a character made using Fuse and Mixamo, and I want to edit the constraints on the bones using UE4 to limit the possible movements of the bones (my goal is to have a realistic ragdoll).
With the physics asset editor, I can easily set a limit on the angles (for example I can say that I don’t want more than 45° of movement between two bones), but I don’t find how to set the min and the max of the rotation.

For instance on the right leg of this character I’ve set that the right leg can have 45° of rotation with the up right leg. But it goes in both direction: the leg can move back or can move forward (cf. pictures). Is there a way to fix this using the editor (i.e. specify that the leg can only go backward)?

You also need to rotate the constraint so that the green(or red, whichever motion you want to use) angle thingy is positioned opposite of how you want the joint to move. Like so:

Hold “alt” while rotating the gizmo in order to change the rest position of the constraint.