Chronic pain is pain that lasts for longer than six months and can be difficulty to describe. It is associated with a flat or withdrawn affect, fatigue, and sleep disturbances. Due to the long-term nature of the pain, chronic pain is not (generally) associated with changes to vital signs like tachycardia and hyperthermia, which are more common in acute pain. Acute pain is more likely to be described as a sharp pain in the ankle.