When we bend forwards, the front of the vertebrae come together, moving disc material backwards. When we move backwards, the opposite occurs: the back of the vertebrae move together, pushing disc material forwards. Movement of the nucleus (the inside of the disc) within the annulus (the outer part of the disc) is normal - to an extent. Unfortunately, it is quite common for the nucleus to be pushed outside its normal limits, resulting in injury. This is typically referred to as a disc protrusion, a disc herniation, or a bulging disc. When discs move out of place, in most cases they bulge backwards or backwards and to the side. In rarer instances, the disc will move to the side, forwards, or forwards and to the side.

Why do discs bulge? The imbalance of forces on our discs throughout our lives is largely to blame. Did you know we bend forwards about 4,000 times per day? And about how many times do we bend backwards? I would say rarely, if ever. Considering that sitting in a slouched posture is also bending the spine forwards, we tend to spend a great deal of time with our spines bent forwards. This not only creates a severe imbalance of forces on the disc, it also overstretches all the supports that are designed to keep this from happening. Is it any surprise then that one day the disc will move far enough to hit something it shouldn't and cause symptoms, signaling to the person that there is an injury?  This is why many patients do not report a traumatic event that created their back or leg pain. (Or, in the neck, their neck or arm pain.) Generally, the injury was years in the making, and then one day the disc went  farther than usual and hit pain-sensitive structures, such as a nerve.

Keeping this anatomy and biomechanics in mind, it follows that to fix an injured disc, patients will RARELY need to perform exercises that bend their spines forwards. (Examples include touching your toes, child's pose, downward dog, crunches, single or double knee to chest, or the figure four stretch.) INSTEAD, most patients need exercises that bend their spines backward, such as standing back bends or lying extension exercises such as cobras or upward dog. Ultimately it is my job to diagnose the patient's injury and then choose the SPECIFIC exercise for that patient that allows him/her to get back on track. -- Laura

I realize I sound like a broken record, but I can't stress this enough: just because something is identified on an x-ray, MRI, or CT scan, does not mean it is causing a problem! Because so many people WITHOUT symptoms have abnormalities, it's clear we can't use imaging to diagnose orthopedic pathology. Instead, patients need a clinical exam in which the structures of the body are stressed in order to determine what the root of the pain/numbness/tingling/etc. is. This chart has some great statistics! Say you're over 40, for example: there's a 68% chance some of your disks are degenerated, a 45% chance some disks have shrunk in height, a 50% chance some disks are bulging, and a 33% chance some disks are protruded. These spinal changes are therefore quite normal as we age and are not necessarily correlated with symptoms. -- Laura

Ever wonder why so many people have their discs move out of place? There's almost double the amount of pressure going through the discs in the low back with slouched sitting compared to standing - not to mention really slouched sitting. And with the amount of sitting most Americans do, all that force can be a recipe for disaster. -- Laura