Polymyalgia Rheumatica is characterized by the subacute onset of aching in the shoulders, hips, and neck, in a symmetrical pattern - and almost exclusively occurs in those over the age of 50. Weakness should not a feature - the limitations in physical activity are typically due to pain. Patients may also feel fatigued. The history may appear to be a bit vague.
On exam, you may find a limited range of motion - but weakness should not be present (unless the symptoms have been going on for a long time and there is atrophy). The symptoms are typically arthralgias rather than arthridites.
Investigations should be mostly normal however inflammatory markers like the Erythrocyte Sedimentation Rate will almost always be elevated. Radiographs of affected joints should also be normal, but ultrasonography or MRI can show bursitis.
Other Important Items: PMR is exquisitely responsive to steroids at low-to-moderate doses, and symptoms may dissolve quickly on as little as 15-20 mg of prednisone. Treatment usually lasts for a few weeks followed by a slow taper. Some patients relapse when tapering, and this is relieved by bumping up the prednisone again. Do not forget to counsel your patient on the side effects of steroid therapy, and to protect their bones.
Relationship to Giant Cell Arteritis: Yes, the two conditions are intimately linked. You can read more about GCA here.
A fantastic review article from Annals of Internal Medicine on PMR and GCA here.