Pathogenic wind changing:
Many diseases are caused by pathogenic wind. Fight between healthy qi and pathogenic factors around the joint leads to flaccidity of tendon and migratory pain.

Pathogenic cold resulting in pain:
Affection by pathogenic cold makes yang qi damage, thus, yang qi fails to warm the tendons, which then contract, resulting in pain.

Pathogenic fire damaging yin:
Fire and heat can damage yin and consume blood, leading to malnutrition of tendon and bone with resultant atrophy and blockage syndrome. Or if the muscle is putrefied by rampant heat, it will cause purulent sore. Or if the rampant heat stagnates, it will lead to formation of tumor.

Qi stagnation:
If the flow of qi is blocked, it will result in pain, which is characteristic of migratory and distending nature.

Blood stasis:
If meridians are blocked by stagnant blood, it will result in pain, which is fixed in certain focus and is of stabbing or cutting nature.

Qi deficiency:
Because of congenitally inadequate essence qi in the kidney and insufficient grain qi derived from food and water after birth by the spleen and stomach, as a result, viscera, tendons and bones become asthenic. Then there may occur shortness of breath, reluctance to talk, lassitude, hyperpnea, spontaneous sweating, thready, weak and forceless pulse.

Blood deficiency:
It may be caused by the failure of the spleen and stomach to produce enough blood or by massive bleeding. Besides the symptoms of pale complexion, palpitation, shortness of breath, numbness of the limbs, vexation, insomnia, and thready and forceless pulse, there may occur contracture of tendon and ankylosis.