Food for older dog with hip displasia

My parents have a rottie mix that's around ten years old and she has been having hip/joint pain. My parents have been feeding her pedigree all her life.

They finally decided to buckle down and switch to a better quality food on top of giving her supplements for her joint pains. I know money is limited a little so I was trying to decide if blue buffalo might be good or if even kirkland has a senior dog food that promotes joint health.

Advice?

I would switch to grain free (totw is probably the most cost effective there) and supp with msm and dgp (dog gone pain which u can usually find pretty affordable on amazon). Fish oil and vit e would be good too.

I don't have any advice about food (except a better one than Pedigree lol), but we well Wapiti Labs Mobility supplement at work, and I've seen it do absolute wonders for dogs with hip and joint issues!

Anything "good" would be ideal. I feed Wellness, THK, and Artisan for my dogs and Shamoo is almost 14 with a ruined knee. More important than the kind of food IMO is to limit the food and cut back as much excess weight as possible.

ETA, My old girl did well on Kirklands grain free.

I supplement with "Joint Oats" (http://www.jointoats.com/index.htm), Fish oil, vit e, and rimadyl on bad days.

I like the Diamond products which makes the food for Kirkland.