Author:

Editor(s):

Updated:

ULY CLINIC

12 Septemba 2025, 01:54:58

Muscle weakness

Muscle weakness is a reduction in the ability of one or more muscles to generate force. It can result from neurologic, musculoskeletal, metabolic, endocrine, cardiovascular, or drug-related causes, as well as prolonged immobilization. Weakness may be localized (specific limb or muscle group) or generalized, and may fluctuate in severity depending on activity or time of day.

History and physical examination

Determine the location and distribution of weakness.
Ask about functional difficulties (e.g., rising from a chair, lifting objects).
Determine onset, duration, progression, and whether weakness worsens with activity or as the day progresses.
Ask about associated symptoms, such as muscle or joint pain, sensory changes, and fatigue.
Obtain medical history, including chronic disease, trauma, family history of muscle disorders, and drug/alcohol use.

Physical Examination

Test muscle strength in all major groups bilaterally, using consistent effort.
Evaluate range of motion (ROM) at all major joints (shoulder, elbow, wrist, hip, knee, ankle).
Test sensory function and deep tendon reflexes (DTRs) bilaterally.
Observe for atrophy, asymmetry, or compensatory movements.

Muscle Strength Grading (0–5 scale)

0 = No contraction
1 = Visible/palpable contraction but no movement
2 = Full movement with gravity eliminated
3 = Full movement against gravity, no resistance
4 = Full movement against gravity, partial resistance
5 = Normal strength, full movement against gravity and resistance

Emergency interventions

Ensure patient safety and prevent falls.
Provide assistive devices as needed.
Protect against pressure ulcers and thermal injury if sensory loss is present.
Implement ROM exercises, splints, or therapy sessions for chronic weakness.
Administer pain management as needed.
Prepare for diagnostic studies: blood tests, muscle biopsy, electromyography (EMG), nerve conduction studies, X-ray, or CT.

Medical causes

Condition	Features	Associated Findings
Amyotrophic lateral sclerosis (ALS)	Progressive weakness, often beginning in one hand	Muscle atrophy, flaccidity progressing to spasticity, fasciculations, dysphagia, drooling, respiratory insufficiency
Anemia	Fatigue and weakness exacerbated by exertion	Pallor, tachycardia, paresthesia, bleeding tendencies
Brain tumor	Weakness varies by location and size	Headache, vomiting, diplopia, decreased visual acuity, LOC changes, hemiparesis/hemiplegia, sensory deficits, ataxia, seizures, behavioral changes
Guillain-Barré syndrome	Rapidly progressive, symmetrical weakness	Ascending flaccid paralysis, sensory loss, absent DTRs, autonomic instability, facial diplegia, dysphagia, respiratory failure
Herniated disk	Weakness from nerve root compression	Severe unilateral low back pain radiating to leg/buttocks, diminished reflexes, sensory changes
Hypercortisolism (Cushing’s)	Limb weakness progressing to atrophy	Moon face, truncal obesity, buffalo hump, striae, hypertension, fatigue, bruising, menstrual/sexual dysfunction
Myasthenia gravis	Fatigable skeletal muscle weakness	Ptosis, diplopia, masklike facies, dysphagia, nasal regurgitation, hanging jaw, respiratory involvement
Osteoarthritis	Chronic disuse leading to weakness	Joint pain, stiffness, restricted ROM
Parkinson’s disease	Weakness with rigidity	Tremor, propulsive gait, bradykinesia, dysarthria, drooling, masklike facies
Peripheral nerve trauma	Weakness in innervated muscles	Paresthesia, sensory loss, loss of reflexes, pain
Potassium imbalance (Hypo-/Hyperkalemia)	Generalized weakness or paralysis	Hypokalemia: cramps, malaise, arrhythmias; Hyperkalemia: flaccid paralysis, irritability, oliguria, arrhythmias
Rhabdomyolysis	Muscle weakness/pain	Fever, malaise, dark urine, risk of acute renal failure
Rheumatoid arthritis	Symmetrical muscle weakness	Joint swelling, warmth, tenderness, pain, stiffness
Seizure disorder	Postictal generalized weakness	Headache, muscle soreness, fatigue
Spinal trauma/disease	Weakness from nerve or spinal cord damage	Flaccid or spastic paralysis, sensory deficits
Stroke	Contralateral or bilateral weakness	Hemiplegia, atrophy, dysarthria, aphasia, ataxia, apraxia, sensory loss, vision changes, altered LOC, bowel/bladder dysfunction

Other Causes:

Drugs: corticosteroids, digoxin, dantrolene, aminoglycosides (especially in myasthenia gravis).
Immobility: prolonged bed rest, casts, splints, or traction.

Patient counseling

Teach proper use of assistive devices.
Explain importance of frequent position changes and rest periods.
Emphasize physical therapy adherence to preserve muscle strength.

Pediatric pointers

Duchenne muscular dystrophy is a major cause of muscle weakness in children.
Monitor for delayed motor milestones and progressive weakness.

References

Barr, J., Fraser, G. L., & Puntillo, K. (2013). Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Critical Care Medicine, 41, 263–306.
Berry, M. J., Rejeski, W. J., Miller, M. E., Adair, N. E., Lang, W., Foy, C. G., & Katula, J. A. (2010). A lifestyle activity intervention in patients with chronic obstructive pulmonary disease. Respiratory Medicine, 104, 829–839.