Most animals will shiver when in pain, so its quite possible your dog is in pain. You can talk to your local vet about giving the dog pain medication to help manage this pain and see if this helps improve it's quality of life over the next year or so, or you can decide to let the dog go and put it down. Sixteen years is a long life, and if your dog is in pain, then it might be better for it to be allowed to pass on gracefully.
If you choose to look at pain management, then there are various options available. Firstly, there are all non-prescription drugs such as aspirin and other pain relievers such as carprofen etc. These reduce pain and swelling, but can cause stomach problems. Steroids such as cortisone or prednisone may be prescribed for serious cases. Opioids such as morphine are prescribed for a lot of pain, but can be addictive.
If you choose to look at pain management, then there are various options available. Firstly, there are all non-prescription drugs such as aspirin and other pain relievers such as carprofen etc. These reduce pain and swelling, but can cause stomach problems. Steroids such as cortisone or prednisone may be prescribed for serious cases. Opioids such as morphine are prescribed for a lot of pain, but can be addictive.