Hmm... I'll have to look into that... I'd always thought of it as being medical-physics territory but it seems I'm wrong. I already have a PhD in neuroscience (colour perception), but could really do with more mathematics.
It gives insights into odd things such as the best form of lighting to do medical procedures under, or colour-vision in aviation, or slight improvements to 3d endoscopy... Part of the problem is that when you're working very long hours it's very difficult to innovate, even though I have a few ideas that I would otherwise pursue.
Was your orthopod acquaintance working in the UK or elsewhere?