If your dog can't walk on it's back leg suddenly, it's most likely due to injury. But sudden lameness can also indicate a neurological issue.
Why is my dog staggering and falling over?, Matthews Emergency Vet
Senior Dog Behavior Changes: What to Expect - Orvis News
Dog Can't Stand Up or Walk on His Back Legs: What Can I Do?
Dog Arching Back and Walking Off Balance: What to Do Next
My dog suddenly couldn't walk on her hind legs. She seems fine now. What's wrong? - Quora
What Is The Best Food For Betta Fish?
17 Causes Of Back Leg Weakness in Dogs
My Dog Can't Walk on Its Back Leg Suddenly: What Happened?
My dog suddenly couldn't walk on her hind legs. She seems fine now. What's wrong? - Quora
Dog Paralysis Back Legs
Why is my dog limping all of a sudden?
What to Do If Your Senior Dog's Back Legs Are Collapsing - The Farmer's Dog
IVDD grades 3 and 4: treatment options and home care – The Rehab Vet
What Is The Best Food For Betta Fish?