Rigidity is characterized by an increased muscle tone (an excessive and continuous contraction of the muscles) which produces stiffness and resistance to movement in joints.[1] Rigidity may be associated with joint pain, with such pain being a frequent initial manifestation of the disease.[1] When limbs of the person with PD are passively moved by others, a "cogwheel rigidity" is commonly seen.[1] Cogwheel-like or ratchety jerks are characterized by the articulation moving as opposed to the normal fluid movement; when a muscle is externally tried to move, it resists at first, but with enough force, it is partially moved until it resists again, and only with further force, will it be moved.[1][2][4] The combination of tremor and increased tone is considered to be at the origin of cogwheel rigidity.[5]