my father is 67 years old and is experiencing leg and feet pain. Mainly from the knee down. He also goes through spouts of feeling weak, drained, tired, no energy, and take a few days to recover. All his blood work came back normal except his muscle enzymes were high. He has had a muscle biopsy and we are waiting on the results from Emory in Atlanta. I have researched possibilities but as you may know the internet can lead you all over the place. I am curious as to an idea of what causes this to happen.
In this age group most common cause of leg and feet pain is weak bones due to deficiency of it. D3. Muscle biopsy mostly going to be an inconclusive investigation.  Start calcium with it D3 and also get x-ray both knees done to exclude osteoarthritis of knee. Thanks