Good morning to you! Sorry to hear that your old girl is having a rough time!
Have you discussed the potential of arthritis with your veterinarian? It's estimated that more than 20% of dogs in the US have arthritis. You might call your veterinarian and ask about safe and approved arthritis medications for dogs. A good exam should also be done, along with blood work and a urinalysis to help determine what is ailing her. When was her last physical?
Frequent urination can be a sign of anything from metabolic type of diseases to urinary tract infections to bladder stones.
Although many of these symptoms are common for older pets, they are also signs that something is wrong and needs to be addressed.
Keep us posted....
frequent urination is likely an infection. however, at that age also consider urinary incontinence due to decreasing estrogen levels. after ruling out bladder infection/ stones/ metabolic problems your vet may want to try estrogen supplement
the arthritis can be eased with new non-steroidal meds from your vet. reduce her weight and try some physical therapy on the affected joints.