Based on my experience, I had a joint bank account with my mother because I'm living abroad and I need someone to be able to do bank transactions on my behalf while I'm away. I submitted our joint bank account with the following documents: (1) letter from my mother stating that I own the money (2) valid ID with photo of my mother with her signature (3) proof of remittance to show that I'm really sending money on that account.
As long as you can justify why you have a joint account and proof that you own the money, it's not a big deal.
Now, I'm a PR.