Acute: Of short duration and relatively severe.

Acute Back Pain: Back pain that lasts a short while, usually a few days to several weeks. Episodes lasting longer than three months are not considered acute.

Acquired: Developed after birth. Not hereditary or congenital.

Adjustment: A specific directional thrust maneuver or application of forces applied to the spine with the intent to improve the biomechanical and neurological components of spinal function and designed to improve the integrity of a joint. In the Chiropractic profession there are over 60 separate and different ways to give an adjustment. They can be categorized into 1) force, 2) minimum force and 3) non-force. A Chiropractic adjustment is performed by using the hands or an instrument to gently "adjust" fixated vertebra and allow for proper motion and position. Because chiropractors work on a variety of people from newborns to the elderly, gentleness is always a priority.

Afferentation: The process of stimulating receptors of a specific type from the peripheral nervous system into the central nervous system.

Ankylosis: Fixation of a joint in a specific position by disease, injury, or surgery. When surgically created, the aim is to fuse the joint in the position which is best fro improved function, not necessarily improved structure.

Anomaly: A marked deviation from the normal standard, especially as a result of congenital or hereditary defect (s).

Annulus Fibrosus: The tough outer ring of a spinal disc.

Arthritis: Refers to an inflammatory and degenerative condition of bones and joints (to include the cartilage) which may create spurring. It can occur anywhere in the body, including the spine. It can result in joint disfigurement and restricted joint mobility. Categorized into as many as 12 types, but the two most common are osteoarthritis caused by biomechanical stresses and injury, and rheumatoid arthritis which is a condition of improper immune function.

Avulsion: Tearing away of tissue, usually due to direct trauma or athletic injury. Ex: A nerve can be avulsed by an injury. An avulsion fracture is a tearing away of part of a bone by the tendon of a muscle.