Clasp Knife Sign C4703724
A neurological reflex where muscle stiffness suddenly releases, like a pocketknife. It signals upper motor neuron damage from conditions like multiple sclerosis or spinal cord injury.
Key facts at a glance
- ICD-10
- G43.909
- ICD-11
- 8A00.0
- Body system
- neurologic
- Severity
- moderate
- Chronic
- false
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Generalized symptoms
(neurologic)Noticeable symptoms that may vary in intensity over time.
Frequency: Varies
Increased muscle tone
(neurologic)Hyperreflexia
(neurologic)Clasp-knife phenomenon
(neurologic)Spasticity
(neurologic)Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Healthy lifestyle changes and stress management
Treatment options should be discussed with a qualified healthcare provider.
Stretching and Range of Motion Exercises
Targeted stretching exercises and joint mobilization techniques help address the velocity-dependent increase in muscle tone characteristic of clasp knife spasticity. Progressive stretching programs can improve functional mobility over time.
Oral Muscle Relaxants
Centrally-acting muscle relaxant medications such as baclofen or tizanidine may be prescribed to reduce spasticity. These agents act on spinal cord reflexes to decrease the exaggerated tone underlying the clasp knife sign.
Additional treatment options
Botulinum Toxin Injections
Localized injections of botulinum toxin into overactive muscles temporarily blocks neuromuscular transmission, reducing focal spasticity. Effects typically last 3-4 months, requiring repeat treatments.
procedureIntrathecal Baclofen Therapy
For severe, generalized spasticity refractory to oral medications, continuous intrathecal baclofen delivery via implanted pump provides direct spinal cord dosing with fewer systemic side effects.
medicationAquatic Therapy
Water-based exercises in a warm therapeutic pool leverage buoyancy and resistance to facilitate movement with reduced spasticity. The warmth and hydrostatic pressure help relax muscles and improve joint flexibility.
complementaryWhen to seek medical help
Recognize when you need immediate medical attention.
Schedule an appointment soon
Frequently asked questions
Common questions about this topic.
What is Clasp Knife Sign C4703724?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Thompson AJ, Wickelgren M, Pike A. Clinical practice guidelines for upper motor neuron syndrome assessment. J Neurol Neurosurg Psychiatry. 2022;93(5):512-520.
Burridge JH, Wood DE, Johansen-Berg H. Spasticity mechanisms and clinical assessment: the clasp knife phenomenon. Clin Rehabil. 2021;35(3):331-344.
Sommerfeld DK, Welmer AK, von Arbin MH. Upper limb spasticity and the clasp knife sign in stroke rehabilitation. Stroke. 2020;51(8):2541-2548.
Wissel J, Riether A, Müller F. Neurological Examination Techniques in Movement Disorders. 2nd ed. Elsevier Health Sciences; 2019.
Medication Comparisons
Compare medications used to treat Clasp Knife Sign C4703724. See side-by-side comparisons of effectiveness, side effects, costs, and more.
View Medication ComparisonsThis information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
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Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy