When a vertebrae becomes misaligned or moves out of its normal position, this is referred to in the chiropractic profession as a subluxation. Subluxations can be caused by a wide range of issues ranging from a minor slip or bump to a car accident or any sudden trauma. When a vertebrae is subluxated, it begins to put pressure on nerves, blood vessels and everything around it. This pressure comes with a price. The subluxation interrupts the natural pathways that the messages sent from the brain need to be clear in order to be completed properly.
As time goes by and a subluxation remains untreated, the spine and surrounding features such as discs can begin to degenerate. This degeneration becomes more difficult to reverse as time goes by as the surrounding muscles, nerves and bones begin to adjust to the new shape. The body is an amazing machine. It will start to accommodate these changes by compensating in other areas. The longer this goes on, the more difficult it is and the longer it takes to get back to near perfect position.
See the segment on spinal degeneration to see the end result of a subluxation to the spine.