Viva trap: when they ask about a condition you've never heard of

In my FRACS structured viva, I was asked about a rare inherited connective tissue disorder and its orthopaedic implications — something not in any textbook I'd read. I panicked and froze, which cost me marks. After reflecting, I realised the examiner was testing my reasoning framework, not recall: state what you don't know, work from basic science principles, and think aloud. Saying 'I'm not familiar with this specific entity, but based on the name and the distribution described, I would approach it by considering...' would have been far better than silence.