The spine is made up of individual bones called vertebrae, which are separated by rubbery cushions called discs. They are stacked atop one another from the pelvis to the base of the skull. The discs act as shock absorbers to minimize the impact of movement. They support upper-body weight and muscle activity allowing for motion such as bending and flexing. A disc is like a jelly donut, with a soft center called the nucleus pulposus, encased within a tough exterior called the annulus fibrosus. The annulus is like an onion, made up of several layers, which contain the nucleus and distribute pressure evenly across the disc.
Just like other ligaments, the discs can be injured. The annulus can tear or rupture anywhere around the disc. If it tears and no disc material is ruptured, this is called an annular tear. The outer third of the disc’s annular ring is innervated with nerve fibers and is highly sensitive to pain. This tear will heal with scar tissue over time but is more prone to future tears and injury.
Most annular tears are due to the natural aging process, but they can also develop by any type of back trauma, such as the force of a car accident, a fall, or a sports-related injury.
Predominant symptoms in many patients with an annular tear in the low back include midline back pain in excess of leg pain. Other symptoms include numbness, loss of sensation, and diminished strength. Symptoms are often worse when sitting compared to standing, and positions that load pressure on the disc (coughing, sneezing, forward bending, and lifting) tend to aggravate symptoms.