Understanding low back pain

What is low back pain?

Among MSK injuries, low back pain (LBP) causes the highest burden with a prevalence of 568 million people in the world suffering from it. LBP is also the main reason for a premature exit out of the workforce. According to The British Pain Society, it costs an astonishing £10 billion on the UK economy. LBP is defined as pain arising from the lumbar spine, which can be divided into two big categories: “specific” and “non-specific”.

Specific LBP accounts for 5% of the total cases.

Of this percentage, 4% is due to RADICULOPATHY (see the next section below for more information) and 1% is due to RED FLAGS, serious conditions that can present as musculoskeletal pain but require urgent medical attention. These Red Flags are: Tumor/Cancer, Infection, Fracture, Compression Pathology (e.g. Causa Equina Syndrome or Myelopathy), Inflammation (e.g. Spondyloarthropathy) and Metabolic disease (e.g. Osteoporosis). Physiotherapists must always screen for serious pathology at the beginning of the consultation and, if there is suspicion, onward referral to doctors and/or Accident and Emergency will be made.

Non-Specific LBP accounts for the remaining 95% of the total cases.

The term “non-specific” means that it not possible to identify the exact cause of the pain. Surprisingly for many patients, a definite diagnosis cannot be achieved even with radiological investigations (such as X-Rays or MRI scans). Having said that, transitory changes in specific structures of the spine (discs and joints) can underpin the onset of pain in most individuals (see below).

LBP is usually categorized in 3 subtypes based on the duration of the pain: ACUTE (less than 6 weeks), SUB-ACUTE (between 6 and 12 weeks) and CHRONIC (longer than 12 weeks).

What can cause acute low back pain?

In most cases, people suffering from LBP who attend physiotherapy clinics will have a pain either discogenic or arthrogenic in nature.

Discogenic LBP originates from the discs of the spine when they have sustained specific changes overtime, such as dehydration or degeneration. These changes will initiate a cascade of peripheral and central events ultimately resulting in the perception of pain. However, you must not be fooled: disc dehydration/degeneration occur in every individual in response to aging and load exposure overtime and having some minor alterations in your spine does not mean that you will feel pain. In fact, discs are designed to modify their shape in response to sudden or repetitive load, acting as “shock-absorbing elements” of the spine. Minor protrusions or herniations are present in most individuals, and they will neither create pain nor impact on people’s ability to function. However, even if disc changes do not compromise spinal health in most cases, specific types of alterations can underpin the onset of LBP. For instance, when the disc bulges significantly out, it can sometimes result in one of the following:

a narrowing of the spinal canal with potential compression of the spinal cord (SPINAL STENOSIS);
an inflammation that irritates the exiting nerve root (RADICULAR PAIN);
a compression of the exiting nerve root leading to alterations of the neural function, such as pins and needles, tingling, numbness, loss of power and reduced sensitivity (RADICULOPATHY).

Arthrogenic LBP originates from the joints in the spine called facet joints. This is more common in the aging population as joint pain is often the result of age-related arthritis, which can affect not only the joint itself but also its innervation, producing both local and radiating pain.

What can cause chronic low back pain?

In general, 90% of LBP cases resolve within 6 to 8 weeks with appropriate physiotherapy. However, in some cases symptoms can continue for longer and, sadly, some individuals will have long-standing pain. Chronic LBP occurs when the impairment is more localized in the central nervous system than in the musculoskeletal system. This happens because our nervous system is “plastic”, where neural plasticity refers to the ability of the nervous system to change its activity in response to internal or external stimuli by reorganizing its structure, functions, or connections. Stimuli that can trigger this include bad prolonged postures, wrong repetitive movements, traumas, strains and surgery. In chronic pain states, these stimuli will produce a cascade of events in the body that will ultimately affect the nervous system. Examples of these events are:

Tonic and persistent stimulation of nociceptors (nociceptors are sensory receptors that detect signals from damaged tissue);
Altered excitability of nerve fibers (nerves start firing electric impulses randomly and spontaneously rather than in responds to a specific stimulus);
Modifications of ion channels with consequent altered signal transmission (transmission of a signal within a neuron is carried out by the opening and closing of ion channels; alterations of these channels will cause abnormal transmission of signals from the periphery to the central nervous system and vice versa);
Up-regulation of specific genes (neurons will increase the expression of specific genes which in turn will amplify the number of receptors in their surfaces: with more receptors, neurons will become more sensitive to specific signals, thus responding more frequently than what they should to peripheral stimuli).

The result of the cascade of events will be the perception of pain despite the absence of an ongoing injury.

Can physiotherapy help with acute and chronic low back pain?

Yes, it can. Physiotherapy uses a series of interventions to help people reducing or eliminating pain from their back. For chronic pain conditions, it cannot always be possible to get rid of the pain completely, but improvements in functionality, mobility and quality of life will be achieved with the right therapeutic approach. Management strategies used in physiotherapy include:

Provide people with education, advice and information about their problem, tailored to their needs and capabilities to help with self-management strategies
Prescribe bespoke exercises
Use manual therapy techniques (spinal manipulation, mobilization, soft tissue techniques and massage)