Muscle strains and spasms - Aches and pains, commonly called "lumbago", usually signal strained muscles, tendons or ligaments or inflamed joints along your spine. If you strain your back, you may feel immediate pain or develop soreness and stiffness later. Muscle spasm usually occurs after some kind of injury (however small it may have been). Spasm is your body's way of saying "Hey - watch out!" It is designed to immobilize you and prevent further damage.
Osteoarthritis - Commonly referred to as "arthritis", this disorder affects nearly everyone past the age of 60. Overloading and injury can slowly deteriorate cartilage, the protective tissue that cover the surface of vertebral joints. Discs between vertebrae become worn and the joints rub together with greater force than normal. The surfaces where they meet - called facets - compress and becomes irregular, the cartilage wears out and gradually your spine stiffens and looses flexibility. Bony outgrowths - called spurs - also develop and the result may be pain.
Sciatica - About 10 people in 100 with back pain may experience "sciatica". Named after the sciatic nerve that extends down each leg from your hip to your heel, this condition can cause inflammation and compression in your lower back and buttock. You may feel pain radiating down to your lower leg. Tingling, numbness or muscle weakness can also accompany this condition.Usually the pain resolves on its own, however, severe nerve compression can cause progressive muscle weakness.
Osteoporosis - The amount of calcium in your bones decreases as you get older. Loss of calcium weakens your bone structure, and in some cases your vertebrae becomes compressed which results in back pain. One in three women older than 50 is affected by osteoporosis. Frequently, structural changes occur in the spinal column that may cause many women to develop a crooked stance or a stooped-shoulder posture called "dowager's hump".
Herniated disc - A "slipped disc" is how you might describe this problem. While the discs don' t really "slip", normal wear and tear, strain or injury may cause a disc to bulge or rupture (herniate). When a disc herniates, parts of the disc can protrude from their normal position between your vertebrae. Pain can result when a fragment of the herniated disc places pressure on an adjacent nerve.