Whenever I see this question in the Internet or I ask it to someone .. people always misunderstand. Maybe because they are not Windows users, or they are Windows users who don't use the keyboard short-cuts.
I always have the same question but I didn't find the answer yet.
In windows, when we use the keyboard short-cuts we mostly use the Menu key in Windows keyboard(see this image):
<== this is the Menu key
When this Menu key is pressed, OS will assume that you right-clicked the highlighted/active element > then it will show you the context menu even if the mouse pointer is not pointing to the highlighted element.
So this feature seems to be missing in Mac OS. And whatever suggested solutions, even Enable Mouse Key it always require you to point/move your mouse pointer to element first, which is meaningless. If I need to use the keyboard short-cut to open the context menu on the highlighted item, why do I need again to move the mouse pointer to it also <== excuse me .. this is not a short-cut!!