Meta files not getting updated?

We are using unity with External Version Control following this guideline http://unity3d.com/support/documentation/Manual/ExternalVersionControlSystemSupport.html

But we have noticed that when we make changes to the scenes and prefabs, those changes are not reflected in the .meta files. Meaning the meta files do not change, and therefore they dont get commited in the update, which causes issues. In general changes are not getting commited.

What can we do to fix this?

Meta files doesn't always change. But I think it's good to save your scene before making the commit, not sure if they update at specific moments. But when they do change, it's very important you commit them.