Motor examination: bulk, tone and strength grading !

Exam technique

A check of muscle bulk, stiffness or floppiness of the muscles, and strength graded from 0 to 5.

Updated 2026-11-01

See it in 3D: Motor cortex · Spinal cord · Grey matter of the cord · Neck nerve roots

What it is

The motor exam assesses three things in order: bulk (muscle mass, wasting and fasciculations), tone (resistance to passive movement) and strength, graded on the Medical Research Council scale from 0 to 5. The pattern of weakness (one side of the body, proximal, distal, one nerve or root territory) points to the site of the lesion.

Landmark anatomy

Upper motor neuron: motor cortex (precentral gyrus) and the corticospinal tract, which crosses at the pyramidal decussation in the medulla.
Lower motor neuron: anterior horn cells of the spinal cord and brainstem motor nuclei, with their root and peripheral nerve.
The basal ganglia and cerebellum modulate tone and smoothness of movement without causing true weakness.

Technique, step by step

Expose the limbs and compare both sides: bulk, wasting, fasciculations and abnormal movements.
With the patient relaxed, passively flex and extend the elbow, wrist, knee and ankle at different speeds to judge tone.
Roll the leg on the bed or lift the knee briskly to detect hypotonia or spasticity.
Strength: ask the patient to hold a position while the examiner pushes; compare each muscle with the other side.
In the arm test shoulder, elbow, wrist and fingers; in the leg test hip, knee, ankle and big toe.
Grade each group from 0 to 5 and record the side.
Functional tests: rising from a chair without the hands, walking on toes and heels, pronator drift.

Medical Research Council (MRC) muscle strength scale

Grade	What is seen
0	No visible or palpable contraction
1	Visible or palpable contraction, no joint movement
2	Moves the joint only with gravity eliminated
3	Moves against gravity but not against the examiner's resistance
4	Moves against gravity and some resistance
5	Normal strength against full resistance

Abnormal findings

Spastic hemiparesis with hyperreflexia: stroke or another lesion of the opposite corticospinal tract.
Symmetric ascending weakness with areflexia: Guillain–Barré syndrome.
Fatigable weakness of the eyelids and proximal muscles without sensory loss: myasthenia gravis.
Cogwheel rigidity with a resting tremor: parkinsonism.

Common errors

The range between grades 4 and 5 is wide; many examiners record 4− and 4+.
Pain, poor effort or not understanding the instruction can mimic weakness.
Judging tone while the patient is tense; tone is assessed only with the muscles relaxed.

Test yourself

Think of the answer, then tap the question to see it.

What MRC grade is a muscle that moves against gravity but not against resistance?

Grade 3.

How does spasticity differ from rigidity?

Spasticity is velocity-dependent and gives way suddenly (clasp-knife), typical of the upper motor neuron; rigidity is equal through the whole range (lead-pipe or cogwheel), typical of the basal ganglia.

What does symmetric proximal weakness without sensory loss suggest?

A myopathy or a neuromuscular junction disorder; the patient struggles to rise from a chair or climb stairs.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of the clinical exam

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: How To Assess Muscle Strength (MSD Manual Professional Edition, 2024); How To Assess the Motor System (MSD Manual Professional Edition, 2024); 16.4 The Sensory and Motor Exams (OpenStax, Anatomy and Physiology 2e, 2022).

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Representative model, for educational purposes only.