No shortcut to open contextual menus on OS X?

I’m really surprised! After years of experience with different Windows and Linux versions it’s getting normal for me to open contextual menus with Shift+F10 or the special context key if a mouse is not available. But yesterday while doing some work on bug 403602 I noticed that there is nothing for OS X? What about handicapped people who aren’t able to use a mouse or even use a screen reader? How do they access the context menu?

I asked several people who are still working on OS X for a longer period of time. But no one was able to give me a hint. So I started searching the web. I got this nice shortcut overview but no system wide shortcut is given. Now, while writing this post, I found this HIG document from Apple. It’s quiet interesting but once again a keyboard shortcut isn’t mentioned.

I’ll stop searching right now and hope that someone, who reads my post, could help me. I would be deeply grateful. Thanks!