1. Core Concept
Hoover's sign is a physical exam maneuver used to help differentiate organic leg weakness from functional (non-organic) leg weakness , often seen in Functional Neurological Disorder (FND) or conversion disorder.
2. The Principle
The test is based on a normal, involuntary synergistic movement: when a supine patient flexes one hip (by trying to raise that leg), they automatically and involuntarily extend (push down) the contralateral hip to brace themselves. This is known as a "associated movement."
- Organic Paralysis: This associated movement is absent. The patient cannot voluntarily lift the "good" leg, and the "bad" leg does not push down.
- Functional Paralysis: This associated movement is preserved but disconnected from voluntary effort. The patient doesn't voluntarily push down with the "bad" leg when asked to lift the "good" one, but the automatic movement occurs.
3. Indications for Use
- A patient presenting with unilateral leg weakness or paralysis.
- When the clinical picture is inconsistent or there are positive signs of a functional disorder (e.g., give-way weakness, bizarre gait).
- To provide objective evidence for a functional component to the weakness.
4. How to Perform the Test (Step-by-Step)
Position: Patient lies supine on an examination table.
Part A: Testing the "Bad" (Weak) Leg
- Place your hand under the heel of the patient's "good" (strong) leg. This is your sensing hand.
- Ask the patient to press down with their "bad" (weak) leg ("Press your weak leg down into the bed as hard as you can").
- Normal/Organic Finding: You will feel firm downward pressure in your sensing hand under the good heel (the associated movement of hip extension).
- Functional Finding: You will feel little or no pressure in your sensing hand, indicating a lack of genuine effort from the "bad" leg.
Part B: Testing the "Good" (Strong) Leg
- Keep your sensing hand under the heel of the "bad" (weak) leg.
- Ask the patient to lift their "good" (strong) leg ("Lift your good leg up off the bed, keeping your knee straight").
- Normal/Organic Finding: You will feel firm downward pressure in your sensing hand under the weak heel (the involuntary associated movement).
- Functional Finding: You will feel little or no pressure under the "bad" heel. The patient may even flex the "bad" hip (a true paradox), demonstrating that the motor pathways are intact but not being used voluntarily.
5. Interpretation of Results
|
Test Component |
Normal / Organic Weakness |
Functional Weakness |
|
Press down with BAD leg |
Positive reinforcement: Strong downward pressure felt under the GOOD heel. |
Negative: No pressure felt under the good heel. |
|
Lift up with GOOD leg |
Positive reinforcement: Strong downward pressure felt under the BAD heel. |
Negative: No pressure (or paradoxical flexion) felt under the bad heel. |
A "Positive Hoover's Sign" for functional weakness is when the test is negative—i.e., the expected associated movement is absent.
6. Key Advantages
- Objective: Provides a physical sign, not just a subjective report.
- Reliable: Has good inter-rater reliability when performed correctly.
- Bedside: Requires no special equipment.
- Diagnostically powerful: A clear positive sign is strongly suggestive of a functional etiology.
7. Important Caveats & Pitfalls
- False Positives: Can occur with pain (e.g., severe back or hip pain), apraxia, profound weakness (e.g., complete spinal cord injury), or lack of patient understanding.
- False Negatives: A savvy patient may learn to fake the sign.
- Not a Standalone Test: Must be used in the context of a full neurological exam and history. It is one of several "positive signs of functional weakness."
- Communication is Key: Deliver instructions clearly and neutrally. Avoid implying you are testing for "faking."
8. Classic Phrasing for Note
"Hoover's test was positive for functional weakness: absence of expected hip extension in the right leg when flexing the contralateral hip."
