I well remember my own mother holding her arm straight out in front of her and kicking up her foot to touch her fingers. She was in her seventies and I had seen evidence myself of her flexibility as she gamely hauled herself up into the attic space to locate something stored away.
She also peddled on an exercise bike because as she said, "once your knees have gone, that's it!" She must have been doing something right because she lived until she was 99 years and six months old, still cooking every day and looking after her bachelor son. So it's no great surprise that Hubby and I believe the same.
Flexibility is key to everything we do and it really doesn't take many minutes in the day to circle hips and shoulders, knees and ankles. Posture is everything and you can do no better than study The Alexander Technique in which you imagine you are a puppet on a string with your head held vertical and not thrust forward like a turkey. Keep your thigh muscles strong too so that they can propel yourself out of your chair without too much difficulty.
Years ago, we were always encouraged at school to stand with chest pushed forward and shoulders back which actually forces a rather unnatural curve to the base of the spine. Rather, the pelvis should be thought of as a shallow basin tipping slightly forward so as to contain all our intestines comfortably and keeping that niggly sacrum from contracting and squeezing our nerves!
If you have trouble with your knees and/or ankles, try gently rotating them on a regular basis and elevate your legs above heart level if possible to take down any swelling.
When my old Mum, near the end of her life, finally consulted a doctor, they had no records for her as she had never been. She had always taken responsibility for her own health. Yes, she may have been fortunate, or have had good genes or whatever, but she never swallowed pills unnecessarily nor (obviously) dashed off to the surgery at the slightest twinge. I too am of the same opinion that given a little time, the wonderful organism that is us, each with our own complex chemical factory within, will generally be able cope with most situations.
I am not a doctor, but I don't have to be to know that by getting myself outside for about twenty minutes a day to soak up natural vitamin D, and sticking to a regular exercise regime, I am helping myself breeze into a happy and healthy old age. For as long as I am able, I shall certainly carry on using it, as I try not to lose it!