Senior Greyhound with sudden onset mobility issues

Hello -

Our senior greyhound has had some mild arthritis for several months. To help manage we use Rimadyl as needed as well as a Joint supplement.

We had her stop doing stairs to the second floor about a month ago when we started noticing some hesitation to go up and down.

About 2-3 days ago she suddenly lost nearly all range of motion in her back legs and front wrist. I eventually had to carry her in and out of the house to go to the bathroom and she skipped going #2

After the bathroom challenges we spent a couple hours in the vet ER last night. They noted all vitals were stable. Ruled out things like Lyme disease. They considered her arthritis mild to moderate and prescribed a daily rimadyl dosage, added amantadine daily and administered an opioid shot.

The shot + New meds made maybe a 10% difference. Not much range of motion in her front legs and very labored walking and limping still.

Those who have experienced similar issues with their greyhound what helped the most? What suggestions can you offer? Any advice here? Seems so sudden compared to where we were just a couple weeks ago.

Thanks in advance