Low back pain is an extremely common condition with some studies showing that 80 per cent of people have had at least one episode of low back pain during their lifetime. While most episodes of such pain eventually resolve themselves, in a small percentage of people, it becomes chronic. This is a major cause of disability and lost productivity and has significant costs
to the society.
The lumbar spine is made up of five vertebrae separated from each other by the intervertebral discs which act as shock absorbers. The vertebrae are joined by the zygapophyseal (facet) joints formed by the articular processes of adjacent vertebrae. The arrangement of the vertebrae forms the spinal canal which houses the spinal cord and the nerve roots.
The neural foramina are also formed by the arrangement of the vertebrae and these provide passage for the nerve roots which supply muscle power and sensation to the back and lower limbs. The arrangement of the facet joints allows flexion and extension of the lumbar spine but limits rotation and this limits rotational stress on the discs.
Ligaments assist in providing stability to the lumbar spine and the muscles of the lower back extend the spine. The actions of these muscles, coordinated with the actions of muscles in the abdomen, hip girdle and pelvic stabilizers contribute greatly to core stability, which plays a great role in protecting the spine from excess loads.
There are many causes of low back pain but some of the more common ones include:
· Mechanical low back pain
· Facet arthropathy
· Discogenic pain
Mechanical low back pain is the diagnosis that best suits the majority of persons who present with low back pain. In these patients, there are likely multiple possible factors contributing to the pain such as:
· Poor core muscle strength
· Poor flexibility
· Habitual poor posture
· Degenerative spinal changes as a result of aging
Experts believe that abnormal movement patterns and alignment of the segments of the spine leads to minor stress on the spine which later leads to major stress and degeneration of the spine, leading to pain.
Facet arthropathy is the presence of changes associated with osteoarthritis (OA) in the joints of the lumbar spine. The degenerative process follows a similar pattern as that described for OA and is a result of aging and repetitive microtrauma. It results in an enlarged joint which is a source of low back pain. The enlarged joint can also make the passages for the spinal cord and nerve roots narrow and potentially compress these structures, leading to other problems.
Discogenic back pain arises from the intervertebral disc and occurs as a result of degeneration of the disc due to repetitive microtrauma. Tears in the disc may lead to internal disc disruption where the nucleus pulposus (gelatinous centre of the disc) breaks down. This causes loss of disc height which leads to spinal instability and increases the likelihood of nerve
It also leads to instability of the facet joints which can result in or worsen OA. The nucleus pulposus may also be squeezed out of the disc in a process called disc herniation. This may cause irritation of the nearby nerve root by direct pressure or from release of irritant chemicals. Dysfunction of the nerve root may occur as a result and this is known as a radiculopathy (nerve root damage). This results in leg pain more so than back pain, possible weakness and abnormal sensation in the leg.
Spondylolysis is a common cause of low back pain in young sportspersons. It is caused by a stress fracture of the pars interarticularis due to repetitive hyperextension of the spine, especially if combined with rotation. It is common in gymnasts, tennis players and young fast bowlers among others. The pain is worsened with spinal extension and alleviated by rest.
Proper management of low back pain requires a thorough evaluation so that an accurate diagnosis can be made. The foundation of back pain treatment is physical therapy with particular focus on core stabilization and this may be all that is needed for mechanical low back pain. Pain control with oral medications, modalities, local muscle injections or acupuncture may also prove helpful. However, someone with facet arthropathy or spondylolysis will likely need modifications to their exercise programme so extension can be limited as it would worsen the pain during therapy.
Persons with leg pain being more problematic than back pain likely have nerve compression and may need investigations such as an MRI or nerve testing. Other measures may be needed to manage the problem and these may include spinal steroid injections or surgery in some cases.
Low back pain which doesn’t resolve within two weeks should be properly evaluated so you can get on the road to regaining optimal physical function.
(Dr Shane Drakes is Specialist in Physical Medicine & Rehabilitation and Sports Medicine. He can be contacted at firstname.lastname@example.org)