Articular neurology has provided
much of the background to understanding
the effect of passive movement
in modulating pain. The type I,
11, and I11 mechanoreceptors located
in joint capsules and ligaments are
stimulated by active and passive joint
movement.16 Type IV nociceptors are
completely inactive in normal situations,
but are stimulated by excessive
mechanical stress or by chemical imtants.16
The gate-control theory postulated
by Melzack and Wall in 196517
proposed that an afferent barrage
from the joint receptors could modulate nociceptive afferent input by inhibition
occurring primarily at the spinal
cord level but influenced to some
extent by higher centers