Why would you have an MRI?

[demotedreally]

An older man I have some responsibility for is having an MRI this week. He says it is part of routine tests but I'm not sure if that is a routine test.

Why do people have MRIs?

I damaged my knee, and they did an MRI to decide if I needed a TKR (I did)

I have them regularly to check the progress of a neurological disease. Other family mehave had them for a salivary duct, back issues and joint issues. You cannot rule much in or out.

I've done one to assess possible surgery on an impacted tooth. It ended up ruling it out as it's touching a nerve. Was told by the first professor in surgery he'd never seen sth like that and he'd been working for 30 years, he said people can work a lifetime in the business and not see one. Another professor decided I had to be wrong and it wasn't possible, he made take the MRI to him and then he was too gobsmacked when he saw it. The technician who did just said "wow, I'd never seen sth like that"! haahhah! Lucky me!
Jokes aside I'm doing another one this week to check out how everything's aligned in my foot. X-rays picked up inflammation but after treatment it's ended up not being plantar fasciitis so doctor needs a better look to see the cartilage, tendons and all the wee bits inside!

MRIs are mostly used for seeing if there are structural changes in soft tissue (like ligaments, muscles, the presence or absence of something)
Xrays are better at hard structures like bones

You really need to know what part of his body is being scanned to narrow it down, otherwise there are just too many option