As the lower five nerve roots exit the spinal column, they join to form the sciatic nerve. Sciatica refers to pain that develops as a result of compression or irritation of this nerve. The nerve roots come together to form the sciatic nerve close to the spine in the upper region of the hip and travel down the back of the leg all the way to the foot. As the nerve travels along the back of the hip, thigh, knee, and calf, it must pass between, and in some cases through, the muscles in these regions. As long as the muscles are loose and flexible and the nerve is able to freely glide along these muscles, the nerve remains healthy. However, if the nerve becomes compressed or irritated at any point along its path from the spine to the foot, sciatica pain can develop.
Sciatica refers to a group of symptoms that occur as a result of injury and irritation to the sciatic nerve. Sciatica is not a specific diagnosis and does not indicate what is causing the nerve irritation; there are many conditions that can cause the sciatic nerve to become injured. One common misconception is that sciatica always results from a disc herniation in the lower back. Although a disc herniation can result in sciatica symptoms, it is one of the less-common causes of sciatica; In fact, it is much more common for sciatica symptoms to develop as a result of problems in the muscles of the hip and leg. Because the sciatic nerve travels between the muscles of the hip, thigh, and calf, when any of these muscles become excessively tight or restricted, they can compress the nerve and prevent the nerve from gliding freely between the muscles. As this happens, the nerve becomes irritated and symptoms of sciatica develop. A complex system of muscles ensures proper movement in the hips and protects them from injury. It is not uncommon for small amounts of strain and imbalance to develop in the muscles of the hip as a result of excessive or repetitive use associated with some sports or occupations, muscle imbalances, prolonged sitting, previous injury, or lack of stretching and exercise.
Over time this strain can develop into what is known as micro-trauma. Simply stated, micro-trauma is very small-scale damage that occurs in the muscles, tendons, joint capsules, and ligaments in response to small levels of strain. Initially, micro-trauma is not painful, but may be perceived as a mild ache or tightness in the muscles. Although small, this damage needs to be repaired. The body responds to micro-trauma in a predictable way: by laying down small amounts of scar tissue to repair the area. Over time this scar tissue can build up and accumulate into adhesions. As these adhesions form, they affect the normal health and function of the muscles and related joints. In fact, they can lead to pain, tightness, stiffness, restricted joint motion, and diminished blood flow.
The accumulation of adhesions can also cause considerable strain and irritation to the sciatic nerve, because the adhesions restrict the normal sliding of the nerve between the muscles. Recall that the sciatic nerve passes between and through the various muscles of the hip and leg to remain healthy and must be able to freely slide between these muscles. As adhesions develop they cause the muscles to become tight and restricted, compresses the sciatic nerve, trapping it between the muscles and the muscle layers. In addition to becoming trapped by the tight muscles, as adhesions develop along the nerve’s path, the nerve can actually become stuck to the surrounding muscles. In either situation the ability of the nerve to slide is drastically compromised. When this happens the nerve is forced to stretch instead of slide, which causes the nerve to become irritated.
As the process continues, further strain is placed on the nerve and surrounding muscles, which leads to even more micro-trauma. A repetitive strain cycle begins, causing continued adhesion formation, progressive nerve irritation, and more severe nerve injury if the condition is allowed to continue.