In 2007 I found it more and more difficult to walk down stairs in the morning. I was getting stiffer and made an appointment with GP. Blood tests did not show a raised esr but none the less I was diagnosed with PMR and started on 20 mg prednisalone. This had little or no effect and was raised to 40 which was effective and over a period of a year reduced the steroids to zero. (Also saw consultant rheumatologist who thought it might be psoriatic arthritis).
A while later the symptoms started up again and so back to GP, but his time I asked to be tested for Lyme disease. I was positive and after two months of antibiotics was fine and have remained so.
Lyme is a very good mimic and it is worth checking with ones GP or rheumatologist that one has been tested.