REFERENCE · DIAGNOSTIC TECHNIQUE

Leg Comparisons in Functional Paralysis

Clinician-focused educational reference; use within professional competence, consent and an individual assessment plan.

Purpose and Suitability
Anatomy and Physiology
Preparation and Safety
Performing the Assessment
Interpreting Findings
Explaining the Result
Evidence and Limitations
Media and Accessibility
Research and Sources

Purpose and Suitability

Use this guide to select and interpret lower-limb comparisons in severe immobility. Hoover’s sign already has a dedicated guide; it is linked here rather than duplicated. Hip-abductor and Spinal Injuries Center comparisons have different requirements.

Unilateral: Affecting one side. Bilateral: Affecting both sides.

Choose the test according to the actual movement, opposite-leg capacity and examination constraints. A named sign is not automatically applicable because someone cannot walk.

Anatomy and Physiology

Hoover’s sign compares hip extension requested directly with extension recruited during the other leg’s resisted flexion. The hip-abductor comparison examines related sideways forces. These are movement comparisons, not a direct measurement of the person’s entire motor system. [1][2]

Abduction: Moving a limb away from the body’s midline. Adduction: Moving it toward the midline.

The Spinal Injuries Center comparison concerns maintaining a placed leg position despite difficulty lifting it. It is not the same mechanism as the paired-leg comparison. [3]

Preparation and Safety

Check pain, hip/knee range, injury, joint precautions, comprehension and sufficient movement in the comparison leg. Explain the proposed movements and obtain consent. Use an examination surface and assistance appropriate to the person’s needs.

Do not force range, abruptly release a limb or use standing as a challenge to demonstrate paralysis. Protect the leg throughout positioning. Stop for pain, distress or unsafe movement; document why the test was not completed.

Marked bilateral weakness may remove the useful comparison on which a sign depends. Do not substitute repeated effort or examiner force for that missing condition.

Performing the Assessment

Select the question before the sign

Comparison	Clinical question	Appropriate source route
Hoover’s sign	Does requested hip extension differ from associated extension during the opposite leg’s movement?	Use the existing Hoover’s guide, including its preparation and evidence limits
Hip-abductor sign	Does sideways force change between paired and separate leg tasks in a suitable asymmetric presentation?	Sonoo’s primary description; record both sides and the actual contrast
Spinal Injuries Center test	Can a severely affected leg maintain a safely placed bent-knee position despite inability to lift it?	Yugué’s restricted comparison; consider mechanical support and severity

These are the original inventory’s assessment roles. The table is a selection aid, not a substitute for learning the full examination technique. [1][2][3]

Document what was compared

Record baseline attempted movement, position, examiner support, the comparison task and observed force or movement. Include pain, compensation, mechanical support and any difficulty understanding the request. Describe why the observation is informative, not merely “positive functional sign.”

This draft does not supply a new step-by-step hip-abductor or Spinal Injuries Center protocol from incompletely retrieved primary methods. The original descriptions remain linked for clinician review. A partially understood technique should not be improvised.

Interpreting Findings

For an interpretable positive comparison, explain the specific contrast in the affected movement. A negative or indeterminate result does not settle the whole diagnosis. The opposite leg’s limitations, pain or an altered technique can change what the comparison means.

Maintaining a bent-knee position is not specific to FND across all severities of weakness. In the original Spinal Injuries Center study, most legs with structural disease that could lift the knee also maintained the test position. The restriction to severe loss of lifting ability is therefore central. [3]

Do not infer safe standing, walking or transfers from an examination-bed finding. Ask separately what support, repetition and recovery are needed in ordinary activity.

Explaining the Result

Authored explanation example: “This comparison concerns a particular leg movement. We need to interpret it with the rest of the examination and any other condition affecting your legs. It does not tell us that standing or walking is safe, so we will assess those needs separately.”

If the sign could not be used, explain the reason—for example pain or lack of a suitable comparison leg. An unsuitable test is not a failure by the person.

Evidence and Limitations

Sonoo studied 33 people with leg paresis: 16 classified as functional and 17 with other neurological causes. All were classified correctly in that sample. The original inventory notes the small, unblinded design; this is not evidence of perfect performance in new populations or widespread paralysis. [2]

Yugué studied 96 legs from 48 people with structural spinal-cord disease and 28 legs from 14 people diagnosed with functional paralysis. Among structurally affected legs unable to lift the knee, one of 48 was positive; among those able to lift, 45 of 48 were positive. Legs are not independent participants. The small selected study and historical diagnostic framing limit generalization. [3]

The Hoover study and its small functional subgroup are discussed in the existing dedicated guide. No pooled or universal accuracy estimate is supplied here. Complete primary full-text review for the other two methods remains pending; retrieved primary abstracts support only the study details summarized above.

Media and Accessibility

Any later demonstration must keep both legs, examiner contact and the supporting surface visible. Label the side and movement. The comparison should be continuous, with no edited substitution of a different attempt.

A static diagram can show the clinical question while the full procedural review remains pending. Do not film a falling leg or unsafe transfer for dramatic effect. Provide captions, alt text and a transcript.

Research and Sources

Primary study records were checked for sample and result context. Their historical titles are retained for accurate retrieval, not as preferred language about the person. The original inventory’s wording is preserved in the inventory.

Citation	Figure	Full citation
[1]	—	McWhirter L, Stone J, Sandercock P, Whiteley W. Hoover’s sign for the diagnosis of functional weakness: a prospective unblinded cohort study in patients with suspected stroke. Journal of Psychosomatic Research. 2011;71(6):384–386. FND-CIT-0018. https://doi.org/10.1016/j.jpsychores.2011.09.003
[2]	—	Sonoo M. Abductor sign: a reliable new sign to detect unilateral non-organic paresis of the lower limb. Journal of Neurology, Neurosurgery & Psychiatry. 2004;75(1):121–125. Historical terminology retained in the article title. FND-CIT-0058. https://pmc.ncbi.nlm.nih.gov/articles/PMC1757483/
[3]	—	Yugué I, Shiba K, Ueta T, Iwamoto Y. A new clinical evaluation for hysterical paralysis. Spine. 2004;29(17):1910-3; discussion 1913. DOI. PMID: 15534415. FND-CIT-0166.

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