Under the weather-pressure.
After reading the contentof the "My Peripheral Disorder "Under the weather-pressure" page earlier on this site, RM sent a mail to me from the San Francisco Bay Area of California USA. She and her mother both suffer from polyarticular (many joints) osteoarthritis. Mother is in her 70's and daughter RM is in her early 40's. The area they live in is known for it's "moderate" weather but it is also known for cold, foggy weather.
RM wrote:"We too have noticed our joint pain increases with changes in the weather. What we noticed, like you, was that our pain corresponds more to the "Weather Glass" (water barometer), than to our wall (aneroid, no liquid, clock-like) barometers that match the daily National Weather Service readings (regional barometric pressure).
We found that our pain increasescorrespond to the small pressure changes (when measured on the water barometer) caused by our local micro-climate (i.e. local fog, wind, effects of an approaching storm), rather than the Regional barometric levels. Small regional barometric changes were expressed as large fluctuations in the tube of the weather glass, most likely local pressure changes. (And apparently in the fluids in our joints as well!) It is these local pressure changes that we all seem to be feeling.
Of course,large regional changes (i.e. a "big storm") will cause the weather glass to fluctuate too, with the corresponding pain increases. But it is these little daily fluctuations we notice, such as when the fog clears in the morning, and comes in again at night, that match our pain patterns the best.
My opinion is that the research to date has focused on Regional Barometric Pressure, and has not yet measured the correlations to the local pressure changes/fluctuations."
RM's information about their experience confirms mine, that it is the small falls in local atmospheric pressure that affect our experience of pain. I experience the tightening of my foot muscles and the irritation of tissue in my feet prior even to the rise of the water up the spout of the water barometer and sometime before the weather change. These changes do not show up significantly on the mercury barometer.