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
One thing the McKenzie method does brilliantly (and better than any other patient approach I've come across) is assess the spine as the source of an extremity problem. A simple analogy uses a fuse box. If an outlet is not functioning properly in your kitchen (ie your knee or elbow), you must take a look at the fuse box (ie the spine) to make sure that the overall system is working properly.
Nerves exit at each level of the spine and carry power and sensation to the extremities. We have maps of where each nerve goes and what muscle(s) each nerve innervates. Therefore, if your wrist hurts, the wrist should be examined locally, but so should the neck and upper back since the nerves that control the wrist come from that area of the spine. If one does not fully assess the spine, one is often missing a lot of information, if not the exact source of the patient's problem, In fact, I tell my students in the clinic that over half of what seem to be "extremity problems" are actually problems of the spine. Even if the patient has no symptoms at the spine, the spine needs to be moved repeatedly to end range to discern if it is playing a role. -- Laura
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