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M Swanepoel
06-22-1998, 02:13 AM
Hello to the Arthrologists and Rheumatologists,

Firstly I'm not sure whether it is true that people DO suffer
increased discomfort from rheumatoid artritis during bad weather.
(Anyone know of research?) However it is such a general observation,
that for the sake of argument I'll assume that it is true. (Most
of you will know that increased joint stiffness for example, is
largely perceived due to stretching and resetting of proprioceptive
nerve endings - despite joints not being mechanically stiffer at all!)

Arthritis (as opposed to arthrosis), is of course an inflammatory
condition, in which the temperature of the tissues surrounding am
afflicted joint is raised with respect to the usual local tissue temperature.
This may be observed using a sensitive infrared scanner. The cause
of the raised temperature is a locally increased blood supply, which usually
aids the body to fight an infection - i.e. inflammation.

Now if the temperature on the surface of the skin is generally
decreased, e.g. by cold, wet weather (water conducts heat away from
the body six times more effectively than air), then peripheral
vasoconstriction occurs. We all know that if such vasoconstriction
is pronounced and prolonged, e.g. in one's hands due to snowball
fights, then the subsequent rewarming process can be excruciatingly
painful, probably because the temperature receptors have reset
themselves downwards, and the sudden shock of the blood flowing back
into the peripheral areas produces a greatly exaggerated sensation in
the hands. If there is a similar chronic resetting of the temperature sensing nerve
endings upwards, in inflamed tissue, then presumably a similarly
exaggerated response to cold may result.

The argument against this is that cold usually brings relief to
inflamed tissue, inhibiting the release of kinins actively involved
in provoking inflammation. However there may be a difference between
an acute inflammatory response to temperature changes and a chronic
one.

A second argument would be that chronic inflammation leads to the inflamed
tissue adjusting to a locally elevated oxygen tension due to the increased blood
supply, and that peripheral vasoconstriction causes pain, due to a
condition "perceived" by the local tissue as being slightly hypoxic.

The matter could be more easily understood if some sufferers could
state exactly when the increased pain is noted - out in the cold,
upon warming up again indoors, or simply anytime that there is
increased humidity, regardless of air temperature location. I'd like
to hear what others have to say, especially if anyone has personal
experience a s a sufferer, or has conducted experiments/surveys on
this issue, although I'm not quite sure that this falls under the
title of "biomechanics"!

Mark W Swanepoel
School of Mechanical Engineering
University of the Witwatersrand

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