Pain that hits you suddenly – after falling from a ladder, being tackled on the football field, or lifting a load that is too heavy, for example – is acute pain. Acute pain comes on quickly and often leaves just as quickly. To be classified as acute, pain should last no longer than 6 weeks. Acute pain is the most common type of back pain.
Chronic pain, on the other hand, may come on either quickly or slowly, and it lingers a long time. In general, pain that lasts longer than 3 months is considered chronic. Chronic pain is much less common than acute pain.