A diagnosis of arthritis is one that most of us will get eventually, and one that seems to be used by doctors when they don't know what the problem really is.
It may well be arthritis, but what you want to know is how it is causing your pains.
As mentioned, pain can radiate or be 'referred' to areas that may seem unconnected.
It is good for you to find out what is going on with your body, so you will need someone more specialised that a standard GP.
Try a physiotherapist. They study and understand how the body works to a much higher level, and are far more likely to be able to help than a GP.
You could also try a remedial masseuse-though the physio may also offer this-who can check out and work on errant muscles.
We all need regular maintenance as we age, so don't get alarmed.