Coordination

Akinesia

Inability to initiate movement.

Athetosis

Slow, involuntary, writhing movements that involve greater involvement of the distal upper extremities.

Bradykinesia

Decreased amplitude and velocity of voluntary movement.

Chorea

Involuntary, rapid, irregular, jerky movements involving multiple joints, most apparent in the upper extremities.

Choreoathetosis

Movement disorder with features of both chorea and athetosis.

Dystonia

Sustained involuntary contractions of opposing muscles, which can be repetitive.

Hemiballismus

Large-amplitude sudden, violent flailing motions of the arm and leg on one side of the body.

Hyperkinesis

Abnormally increased muscle activity or movement.

Hypokinesis

Decreased motor response, especially to a specific stimulus.

Rigidity

Increased muscle tone creating greater resistance to passive movement; not velocity dependent.

Lead-pipe rigidity

Uniform, constant resistance as a limb is moved.

Cogwheel rigidity

Series of brief relaxations or 'catches' as a limb is passively moved.

Resting tremor

Involuntary, rhythmic, oscillatory movement observed at rest.

Balance

All forces acting on the body are balanced so that the center of mass is within the stability limits of the base of support.

Postural control

Maintained positions of body parts with respect to each other and gravity.

Vestibular system

Stabilizes gaze during head movements and helps regulate postural tone and muscle activation.