I've always consulted my vet...if it's from an injury , maybe your vet can refill prescription...sorry couldn't give an exact remedy but best wishs for your dog.
If it's arthritis then there are two products called Canine Flex Plus and Hyla Flex with Microfractured Chia. These products work great. But if your dog has undiagnosed pain you should take him to a vet first. Most animals are better handling pain then people.So when they show signs of pain, it's best to get them treatment or vet care right away.
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