How can I apply constraints in pose mode?

Question

I have a simple hinge joint for a primitive knee. I have the upper leg parented to one bone, and the lower leg parented to its child bone. The joint where these two bones connect should only ever rotate on the X axis, and only up to 140°. To accomplish this, I selected the lower leg bone and added a Limit Rotation constraint like so:

However, when I go into pose mode I can still rotate the bone in undesirable ways. I noticed that the constraint seems to be applied to the entire armature, not the specific bone. I only want to make the model easier to pose by constraining the joints to realistic limitations. I've seen videos of people posing models where semi-circle UI appears at the joints in pose mode, and can be manipulated to rotate the bones within certain "constraints"; how can I do this? I assumed that "constraint" was the correct word to describe this feature but apparently not.

Answer 1

You added an "Object constraint", while you should be adding a "Bone constraint". So the whole armature has rot limited, while the bone in its local space is completely free.