Osteoarthritis of the hip or knee in early stages, when it is restricting rather than debilitating can be managed by weight loss, if overweight and occasional paracetamol and a trial of glucosamine and chondroitin (available from most chemists) which have both been shown to be of benefit in mild to moderate arthritis.
To help decide when to see your GP and what they might suggest to do next, the Oxford hip or knee score is a useful tool to help decide what to do next. They score how much your arthritis affects you.
Oxford Hip Score
http://www.orthopaedicscore.com/scorepages/oxford_hip_score.html
Oxford knee score
http://www.orthopaedicscore.com/scorepages/oxford_knee_score.html
General advice about managing knee and hip arthritis can be found at
http://www.nwbh.nhs.uk/knee-osteoarthritis
http://www.nwbh.nhs.uk/hip-osteoarthritis