So how does all of this translate into low back pain? Because of the multidimensional composition of the low back, unlike other joints in the body painful conditions do not move in a sequential pattern and are rarely isolated. For understanding purposes, the different causes have been divided.
Lumbar Muscle Spasms or Strain
As mentioned before the muscles of the low back are typically being pulled into a degree of flexion in those with postural dysfunctions, weaknesses, and symmetrical imbalances. Until such issues are addressed the musculature suffer from strains in resisting these movements. Because the muscles stay in a relatively contracted state due the constant malpositioning of the vertebrae, they use up all available energy and simultaneously are unable to remove waste. As a result trigger point formation (microfiber muscle spasm) occurs. Trigger points themselves can cause painful symptoms due to the local waste byproducts that build up around the muscles. Furthermore, the contracted state of the muscle fibers cause muscle spasms that reduce optimal flexibility and mobility. Micro-spasms also alter the optimal dynamics of the vertebrae diverting stresses where they are less likely to be sufficiently managed. Imbalance in stress results in immediate or future pain.
Additionally gross muscle spasm within the lumbar spine can cause painful symptoms, but muscle spasm typically occurs as a protective mechanism and highlights that an underlying condition or problem may be present.
Facet Joint Syndrome or Dysfunction
Like most other moveable joints in the body the facet joints are surrounded by synovial (or joint) fluid. To maintain their health they must be moved to continuously allow fluid to circulate around the bony articulations. Additionally, movement tells the body that these structures are not being wasted through disuse and their continual upkeep should be maintained. Facet joint dysfunction occurs when the facets become locked or relatively immoveable, reducing mobility and function (20). Due to their directional influence on movement and load(s) within the spine they are designed to redirect forces where they can be sufficiently absorbed by stronger structures. Immobility prevents the facets from completing such function and instead they absorb the forces. To combat this the body will deposit fibrotic tissue across and around the joints for added rigidity and protection (21). In older demographics bony formations will eventually replace fibrotic tissue, further limiting movement and function. In attempting to add protection to the joint, the body further compounds the problem. Swelling, facet sprain, and eventual degeneration of the joint cause painful symptoms (22).
Intervertebral Disc Herniation or Rupture
Each disc is composed of the outer more fibrous structure, the annulus fibrosis, and the inner more gel-like core, the annulus pulposus. When the spine is in neutral position, the disc lies evenly spaced between articulating vertebrae similar to a round discus shaped air filled cushion.
Intervertebral discs become injured through two common mechanisms; postural dysfunction and gross force disruption. Repetitive postural dysfunction occurs when the disc is under low load but remains compressed at the back of the vertebral body forcing the gel-like inner contents forward and placing strain on the outer walls of the disc. High gross force also potentially compresses the disc as mentioned, but because the disc is directly attached to the vertebral body and possess properties that resist movement if a high load is transferred through the spine from a single activity the disc will become strained once stability is compromised. Most commonly discs will become weakened through postural dysfunctions and poor stability, but a single traumatic event will be attributed to actual disc herniation or failure. To visualize this, imagine stepping on and compressing that cushion and the air is forced to the opposite end stretching the outer walls. Eventually the retaining wall of the disc will lose its tensile strength and herniate or protrude. Constant repetitive stresses will cause the walls to rupture releasing the inner gel of the disc into the adjacent spinal structures. Once a disc has protruded, pressure is commonly placed on the nearby spinal structures or nerves. This pressure explains why neurological symptoms are often felt down the extremities in conjunction with the local pain. Further swelling and compression of the damaged vertebral disc compounds painful and neurological symptoms.
Sacro-Iliac Joint Dysfunction
Despite not being a joint with a great amount of mobility, the sacro-iliac joint can cause pain in the lower back if its mechanics become altered. The ilium of the hip should be allowed to rotate anteriorly and posteriorly with thigh/hip and sacral movements. If the sacro-iliac joint becomes fixated, direct stresses are placed through this small articulating joint causing pain and swelling. Long term fixation of this joint will see fatty and fibrous tissue deposits laid down over and around the joint. Additionally, the inability of this minute joint to move places stress on other lumbar vertebrae that must adapt and move excessively to maintain functional range that can have further repercussions on the lumbar vertebrae and the hip.
As discussed previously, the vertebral column is surrounded by ligamentous structures to add further rigidity and support to bony structures. As in all joints, ligaments are the last line of joint integrity and support. In the low back, the ligaments are commonly sprained by repetitive tensile stresses from postural or movement dysfunctions or by stresses placed on them from resulting muscle fatigue or failure at the end of range. This causes painful muscle spasm(s) that aim to protect the injured ligament. Additional ligamentous strains will eventually cause the ligaments to become stiff and lose their elastic properties, further compromising mobility and stability causing other structures to compensate potentially increasing the likelihood of injury to these structures.
Low Back Pain Causes Summary
Although there are many other causes of low back pain it is not within the scope of this article to list and review every one. However, the reason that the above painful conditions are highlighted is due to their ability to be prevented by altering and improving the way in which movement is performed. Typically, the conditions listed above either cause or are byproducts of hypomobility. Because the low back is a structure designed to move and absorb load that has great influences throughout all parts of the body, achieving mobility with stability is key whether the low back is being treated for or to prevent injury. Furthermore, with increasing quality of movement and muscular stability most conditions can be successfully managed. In part 3, exercise techniques and specific exercises will be highlighted, reviewed, and demonstrated that will lead to a healthier and pain-free lower back.
Kyriacos Ioannou (Kyri) is an expert is anatomy, physiology, rehabilitation and massage techniques. He has an Upper Class Second Honors degree in Sports rehabilitation and Injury Prevention, and a Masters in Advanced Sports Therapy and Rehabilitation Sciences specializing in mobility of the lumbar spine. He also holds certifications in kinesio-taping, acupuncture, joint mobilizations and is an NASM certified personal trainer. His wide knowledge base and experience combines a broad spectrum of therapeutic ideas to achieve the optimum goal of health and movement.
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