Jeanne's Sign: Thumb MCP Hyperextension Instability, Chronic Ulnar Palsy, and Dynamic Splinting
In short
Severe chronic ulnar palsy collapses thumb stability; positive Jeanne's sign exhibits marked MCP hyperextension during key pinch requiring dynamic joint stabilization.
In this guide (4 sections)
The Biomechanics and Pathoanatomy of Jeanne's Sign
Jeanne's sign is an advanced biomechanical compensation seen in severe, longstanding ulnar nerve motor paralysis. During lateral key pinch, a healthy thumb maintains slight flexion (approximately 10 to 15 degrees) across both the metacarpophalangeal (MCP) and interphalangeal (IP) joints, creating a stable, rigid triangular arch.
In chronic ulnar nerve lesions, paralysis of the Adductor Pollicis (AP) is compounded by denervation of the deep head of the Flexor Pollicis Brevis (FPB), which is innervated by the ulnar nerve in up to 80% of individuals. With both primary MCP stabilizers non-functional, the patient activates the median-innervated Flexor Pollicis Longus (FPL) to generate pinch force at the tip. Without intrinsic volar muscular support at the MCP joint, the proximal phalanx collapses into marked hyperextension (often exceeding 20 to 30 degrees), creating Jeanne's sign.
Biomechanical Comparison: Froment's vs Jeanne's vs Bouvier's Maneuver
| Clinical Sign / Maneuver | Anatomical Joint Involved | Observed Biomechanical Deformity | Clinical Therapeutic Directive | |
|---|---|---|---|---|
| Froment's Sign | Thumb Interphalangeal (IP) Joint | Acute hyperflexion (> 60-90°) of thumb distal phalanx (FPL substitution) | Indicates loss of Adductor Pollicis; initiate intrinsic retraining | |
| Jeanne's Sign | Thumb Metacarpophalangeal (MCP) Joint | Hyperextension (> 20-30°) of thumb MCP joint during active pinch | Indicates combined loss of Adductor Pollicis AND deep head of FPB | |
| Bouvier's Maneuver | Finger MCP and PIP Joints (Digits 4 and 5) | Manual stabilization of MCP in flexion allows active IP extension | Differentiates simple extensor lag from fixed flexion contracture | |
| Zancolli Lasso Indication | Metacarpophalangeal Joint Palmar Plate | Positive Jeanne's and Froment's causing severe key pinch collapse | Surgical tendon transfer to recreate volar MCP flexion moment |
Standardized Clinical Rehabilitation Protocols and Orthotic Stabilization
- Jeanne's Sign Screening During Functional Pinch Testing: Instruct the patient to pinch a key or dynamometer forcefully; observe the profile of the thumb from the radial side; if the MCP joint bends backward into hyperextension while the tip curls down, document a positive Jeanne's sign and measure the hyperextension angle with a finger goniometer.
- Custom Thermoplastic MCP Flexion-Blocking Ring Splint: Fabricate a small thermoplastic or silver ring orthosis that rests dorsally over the first metacarpal head and proximal phalanx, mechanically blocking MCP hyperextension beyond 10 degrees of flexion while allowing free tip movement.
- Thenar Web-Space Mobilization and Opponens Strengthening: Perform manual stretching across the first web space to prevent adduction contracture; strengthen the median-innervated opponens pollicis to position the first metacarpal in wide palmar abduction for stable grasp.
Frequently Asked Questions
Why does my thumb knuckle bend backward like a rubber band when I try to pinch something?
This is called Jeanne's sign. The deep muscles that normally support the base knuckle of your thumb have been paralyzed by a pinched ulnar nerve. When you pinch hard, the joint has no muscular support, causing the knuckle to collapse backward into hyperextension.
How does a simple knuckle ring splint restore my pinch strength?
When your thumb knuckle collapses backward, you lose almost all your pinch power. A small custom ring splint acts like a solid brace that stops your knuckle from bending backward, instantly channeling all your muscle power straight into your pinch so you can turn keys and hold objects securely.
Is Jeanne's sign a sign of permanent hand damage?
It shows that your nerve has been severely compressed for a long time. However, once the nerve is surgically freed, many patients regain muscle strength. If the muscle does not recover, a minor surgical procedure called a tendon transfer can permanently stabilize the joint.
Related condition guides
Related recovery guides & articles
BookPhysio.in Editorial Team
The BookPhysio.in editorial team writes and maintains this content, checking it against reliable clinical sources. Content follows our medical review policy: general information only, and no page claims a clinical review until a named registered physiotherapist has signed it off.
Read our medical review policy