not only when it is unseasonably cold, but also when it is unseasonably warm.

Apart from being exposed to adverse weather conditions, Painful Obstruction Syndrome can of
course develop also from exposure to other conditions, such as sitting on damp surfaces, wading
in water, living in a damp environment, etc.

Although the only aetiological factor in Painful Obstruction Syndrome is weather, there are other
predisposing factors. First of all, excessive sport or work activities may predispose one to
develop Painful Obstruction Syndrome. For example, excessive aerobic exercise or jogging may
put a strain on the spine and lead to backache. The constant repetition of a certain movement in
one's work is an obvious predisposing factor too, as this causes stagnation of Qi and Blood in an
area which becomes more prone to invasion of exterior pathogenic factors. For example, the
wrists in car mechanics become prone to stagnation of Qi and Blood through repeated use of
wrenches, spanners and screw-drivers.

Another very important predisposing factor is an underlying deficiency of Blood or Yin which
leads to malnourishment of the channels so that they become prone to invasion of external
pathogenic factors. Particularly in chronic Painful Obstruction Syndrome or in the elderly, an
underlying deficiency of Blood or Yin is nearly always a factor. In treatment, it is important not
only to expel Wind, Cold or Damp, but also to nourish Blood or Yin.

Accidents also predispose one to Painful Obstruction Syndrome. An accident causes either
stagnation of Qi (if light) or Blood (if serious) in an area. Even though one may seemingly
recover perfectly well after an accident, some stagnation of Blood may remain in the area. Years
later, exposure to external pathogenic factors leads to the development of Painful Obstruction
Syndrome in that particular area. This often explains the unilateral development of Painful
Obstruction Syndrome as the climatic factors of Wind, Cold or Dampness settle in the area
where there is a pre-existing condition of stagnation of Blood caused by the accident.

Finally, emotional problems are also contributing factors in the origin of Painful Obstruction
Syndrome either by causing stagnation of Qi (such as from anger or resentment) which affects
the channels, or by causing depletion of Qi and Blood (such as from sadness, grief and shock)
which leads to malnourishment of the channels.

Differentiation

Since very ancient times Painful Obstruction Syndrome has been classified according to the
predominant pathogenic factor, i.e. Wind, Cold or Dampness. For example the "Simple
Questions" in chapter 43 says: "The three pathogenic factors of Wind, Cold and Dampness give
rise to Painful Obstruction Syndrome".4(444) Zhang Jie Bin (1563-1640) says: