A person with limb weakness has lost strength in an arm or leg.

Limb weakness can be caused by malfunction of part of the brain or nerves, both of which stimulate muscles to move the limb. The location of the limb weakness can provide a clue to the underlying cause. Whether or not the limb weakness is confined to one-side of the body is also an important clue to the underlying cause.

Limb weakness may be bilateral or unilateral:

• Bilateral limb weakness may involve:
• Both arms
• Both legs
• Both arms and legs
• Unilateral limb weakness may involve:
• One arm
• One leg
• Arm and leg on the same side of the body