Where there is no movement,
there is pain.
Where there is movement,
there is no pain.
This Chinese proverb very clearly suggests that all pain is caused by stagnation, usually of Qi (Energy) or Blood. Therefore, if we manage to move Qi or Blood, the pain will go away.
Think about how often you have instinctively rubbed a painful area of your body, may it be the head, or a joint, or a painful stomach. It is the attempt to 'move' things, to stop the stagnation that is causing the pain. Of course, Chinese medicine differentiates between Qi stagnation, which presents with a dull, possibly moving/wandering pain and Blood Stagnation, which is sharp, knife-like and fixed.
Gentle exercise, acupuncture and herbs are great at moving Qi and Blood in the body. Try it!