Radicular pain (such as sciatica) is a common problem that presents to musculoskeletal physiotherapists and general practitioners. In a recent primary care study in the UK including 609 patients, 60% of people presenting with a combination of back and leg pain were diagnosed with sciatica (1). Due to the high prevalence of sciatica and associated pain and functional limitations, it is vital clinicians can identify radicular pain accurately and differentiate it from other pathologies. Part 1 of this two-part series will aim to help you understand what radicular pain is, how it presents, and outline conditions that can masquerade as radicular pain that could be considered in your differential diagnoses. But first, let’s delve into some definitions, causes and presentations.

Definition and Presentation
Radicular pain is caused by inflammation and/or compression of the lumbosacral nerve roots (L4-S1) and results in a gain in nerve function (2). This refers to an abnormal excitability of the nerve, presenting with paraesthesia, pain, hyperalgesia, allodynia, hyperreflexia, and/or muscle spasms. Pain often presents in the buttock, travelling down the leg and below the knee.

image

This differs from lumbar radiculopathy, which is also a nerve root problem, but results in a loss of nerve function. This means there is reduced impulse conduction which may present as hypoesthesia, anaesthesia, weak/absent reflexes, muscle weakness and/or reduced sensation. Unfortunately for practitioners, patients don’t always fit into these categories and it’s therefore not uncommon for patients to present with features of both conditions, such as a painful radiculopathy (3). It’s also important to remember that true radicular pain is an extremely distressing and painful condition, with some patients reporting a loss of their sense of self (4).

In general, sciatica is poorly defined in the research. Whether you are a physiotherapist fresh out of university or have been practicing for many years, you’ll likely have known or heard of someone complain of sciatica. But, how do we know it is definitely sciatica? How do we know the problem isn’t from the sacroiliac joint, the hip or (god forbid) the dreaded piriformis muscle?! Let’s look into some risk factors and causes of radicular pain to help identify the patients that might have a true nerve root pathology.

Risk Factors
To accurately identify someone with radicular pain, it is important to understand the risk factors and causes of the problem. This was very nicely laid out by Tom Jesson in the Physio Network Masterclass on Radicular Pain. If you want a thorough explanation of the history, pathophysiology and management of radicular pain, be sure to check it out. Tom classified risk factors and causes into two groups as documented below.

Distal (The Kindling):

Smoking
Obesity
Manual work
Work bending down
Driving a lot
Moderate walking
Mental stress
Poor job satisfaction
Proximal (The Fire):

Disc lesion
Spinal/Recess stenosis
Spondylolisthesis
While this is not an exhaustive list, these are important to consider as part of a comprehensive assessment including your subjective and physical exam.

How is Sciatica Diagnosed?
A diagnosis of sciatica is based on clinical presentation, involving the patient’s subjective symptoms and the findings of the physical examination. There is no specific test for sciatica, but a combination of positive findings on examination increase the likelihood (6). Imaging is rarely required to make a diagnosis unless a more sinister pathology is suspected or if the patient has not responded to conservative management as expected (2). However, if the patient presents to your clinic with imaging already completed, then by all means check to see if your exam aligns with the imaging findings. The key signs and symptoms of sciatica include:

Dominance of leg pain (more than back pain)
Location of the leg pain (e.g. below the knee)
Dermatomal pattern
Paraesthesia and/or sensory loss aligning with the spinal root
Myotomal changes
Reflex changes
Leg pain when coughing, sneezing, taking deep breath
Gradual onset
In your physical examination, the below are possible findings:

Unilateral motor weakness (particularly dorsiflexion if L5 is affected, leading to foot drop)
Absent tendon reflexes
Positive SLR (if negative, this reduces suspicion of sciatica)
Positive cross over test
Increased finger-floor distance (>25cm)
It is vital that the practitioner can exclude sinister pathology by screening the patient for trauma, cancer or serious infections. If your index of suspicion is low for sinister pathology, it is worth considering if your primary diagnosis of radicular pain is accurate, or if the pain is coming from somewhere other than the nerve root. Other potential conditions that may masquerade as radicular pain are outlined in the below table (7).