Straight Leg Raise Test

Anatomy and Physiology

The straight leg raise test is basically a provocation test that evidences radicular irritation in the lumbosacral region by lower limb flexion and can be due to multiple causes. Radicular symptoms are primarily produced by nerve root inflammation by surrounding structures.[9] The foramina are formed by the pedicle superiorly and inferiorly, ligamentum flavum posteriorly, disc and vertebral body anteriorly, and this small space normally allows the nerve root excursion of 4 mm, however during the straight leg raise test, this root excursion can be compromised by several factors. Mechanical compression does not always generate radicular symptoms as many patients have asymptomatic foraminal stenosis in magnetic resonance imaging (MRI); therefore, a positive leg raise test may be influenced by nerve root irritation secondary to inflammation as mechanical compression.[10][11]

The straight leg raise test is attributed to Charles Lasegue, a French clinician who described two cases of sciatica aggravated by weight-bearing, hip, and knee flexion in “Thoughts of Sciatica” in 1864. Nonetheless, Dr. Lasegue did not describe the test as a provoked pain; instead, his student JJ Forst described the test in his doctoral thesis in 1881, and it was Forst who considered the pain to be produced by hamstring muscle compression to the sciatic nerve.

Nevertheless, it is believed that a Serbian neurologist, Dr. Lazar Lazarevic, was the first to document the straight leg raise test as it is known today in the article named “Ischiac postica cotunnii,” initially published in the Serbian Archives of Medicine (1880), and republished in Vienna (1884).[12] Dr. Lazarevic described the straight-leg-raising test by explaining sciatic pain by stretching the sciatic nerve based on his experience with six patients. Based on this misinterpretation of the original description, it is recommended to describe the maneuver as the straight leg raise test.

Indications

The straight leg raise test is a commonly used test in identifying impairment in disc anatomy or nerve root irritation. Also, it has specific significance in detecting disc herniation and nerve compression.[13] It can also be used as a neurodynamic evaluation test because it can detect nerve root tension or compression. Following are some of the commonest indications for performing a straight leg raise test:

• Low back pain
• Buttock pain
• Leg pain

Contraindications

The straight leg raise test requires the patient to be in a specific position. It also requires movement in certain joints. The following are some of the contraindications of performing the straight leg raise test:

• The does not give consent for the test
• The patient is unable to lie down straight due to any underlying issues, such as serious spinal disease, advanced scoliosis, etc.
• The patient has advanced knee or hips joint disease making the procedure excessively uncomfortable for the patient

Personnel

The straight leg raise is a very easy test to perform, but the provider should have expertise in performing it correctly, as performing it wrong could lead to patient discomfort and may not yield any reliable results. The following is the list of providers that could perform this procedure:

• Primary care provider
• Orthopedic surgeon
• Neurologist
• Neurosurgeon
• Sports medicine specialist
• Nursing staff
• Physiotherapist
• Chiropractor

Preparation

It is essential to obtain consent from the patient before performing the straight leg raise test. Another important step is maintaining patient privacy and having a chaperone around before performing the test. 

Technique or Treatment

The straight leg raise test is performed with the patient in a supine position. The examiner gently raises the patient's leg by flexing the hip with the knee in extension, and the test is considered positive when the patient experiences pain along the lower limb in the same distribution of the lower radicular nerve roots (usually L5 or S1).

Furthermore, a positive straight leg raise test is determined when pain is elicited by lower limb flexion at an angle lower than 45 degrees. Patients usually request that the examiner abort the maneuver during the test if the pain is reproduced during the leg straightening. The buttock pain is usually relieved by flexing the patient's knee (Figure 1).

Additional maneuvers have been described to enhance the test's sensitivity, such as the Bragaad sign, which consists of concomitant foot dorsiflexion to increase the pain while the examiner completes the leg raise.

An additional maneuver is the crossed straight leg test (crossed over Lasegue), in which the examiner passively flexes the patient's uninvolved limb while maintaining the knee in extension. A positive test is when the patient reports pain in the involved limb at 40 degrees of hip flexion with the uninvolved limb. A crossed straight test is positive with central disc herniation in cases of severe nerve root irritation.[14]

Clinical Significance

Previous analysis of the sensitivity and specificity of the straight leg raise test shows high sensitivity and low specificity of lumbar disc protrusion.[8][15] However, most of the literature is limited by poor quality and is based on surgical case series at a non-primary care level, limiting the external validity of these findings. Also, some studies have shown restricted diagnostic accuracy of neurological examination detecting disc herniation with radiculopathy.[16] As the test demonstrates high sensitivity, it could be useful to rule out lumbar disc protrusion; however, the utility is limited due to low specificity, as it can be positive in ischialgia secondary to other causes.

A straight leg raise test is an important physical examination finding during primary care to assess the need for imaging studies such as X-rays and MRI and the potential need for a referral from primary care to a spine specialist.

This test is also relevant among spine specialists to guide proper treatment options; being positive Lasegue test is a sign of nerve root irritation and possible entrapment, which might require a nerve root injection or surgery.[16][17]

A positive straight leg raising test results from gluteal or leg pain by passive straight leg flexion with the knee in extension. It may correlate with nerve root irritation and possible entrapment with decreased nerve excursion. This clinical neurological test has high sensitivity and low specificity; it is an important diagnostic workup in patients with lower back pain and suspected radiculopathy. This test is relevant to guide referrals among primary care providers and treatment among spinal surgeons, especially when considering a surgical decision.

Enhancing Healthcare Team Outcomes

Low back pain is among the most common complaints in active workers and a significant cause of absenteeism from work. Sciatic pain radiates from the buttocks to the leg and is frequently associated with low back pain. In this regard, a neurological examination is fundamental in distinguishing patients with isolated lower back pain from those with associated radiculopathy. Consequently, early recognition of radiculopathy allows targeted treatment and diminishes disability. 

This maneuver can provide information for many interprofessional team members, including physicians, mid-level practitioners, nursing staff, physical therapists, and chiropractors. Performing this maneuver correctly, when indicated, helps the interprofessional team assess the need for imaging studies such as X-rays and MRI and the potential need for a referral from primary care to a spine specialist. Each team member must record the test result in the patient's health record and report these findings to other team members as appropriate. The best possible outcome for patients with low back pain could never be achieved without the interprofessional collaboration of the various mentioned disciplines. The need for clear communication strategies between interprofessional healthcare members and their patients is key to attaining the best possible standards of care.

Nursing, Allied Health, and Interprofessional Team Interventions

• The nurse can help position the patient before, during, and after performing the straight leg raise test.
• The nurse needs to inform the patient about the follow-up appointments and the care plan designed by the provider.
• The nurse must report untoward changes in the patient's vital signs or pain score to the clinician.

Nursing, Allied Health, and Interprofessional Team Monitoring

• Vital signs
• Pain scores
• GCS (Glasgow Coma Scale/Score)