Make sure they are eating well and see a doctor.
There are many supplements and foods that can help reduce the inflammation and effects of arthritis in dogs, and there are several dietary changes you can make to help combat symptoms of other conditions, such as allergies, that are common to the elderly people can be particularly distressing.
Talk to your veterinarian or nutritionist about putting together an appropriate diet for your senior to prevent weight gain, which can make arthritis worse, and make sure your dog is getting the supplements he needs to fight other conditions avoid those that affect arthritis.
Also, talk to your veterinarian about medications your dog may need to take to treat symptoms that are preventing him from moving. If your dog is having trouble moving, see if hydrotherapy or acupuncture can help him get back on his feet.
These steps will ensure that your walks are beneficial to your dog rather than doing more harm than good.