Motor Strength and Power



Motor Strength and Power





Motor strength and power indicate the capacity of muscles to exert force and expend energy. Decreased strength is weakness, or paresis; absence of muscle contraction is paralysis, or plegia. Weakness may cause loss of the speed, rapidity, or agility of movement and a decrease in the range, or amplitude, of movement before there is loss of power to formal strength testing. Other manifestations of impaired motor function include fatigability, variation in strength on repeated tests, diminished range and rate of movement, loss of coordination, irregularity and clumsiness of motion, tremulousness, loss of associated movements, and lack of ability to carry out skilled acts.

While judgment of the force exerted in either initiating or resisting movement is the major criterion in the evaluation of strength, observation and palpation of either the contraction of the muscle belly or its movement of its tendon may be helpful adjuncts. The contraction of an extremely weak muscle may sometimes be felt when it cannot be seen. In nonorganic weakness, contraction of the apparently weak muscle may be felt when the patient is asked to carry out movements with synergistic muscles, or the antagonists may be felt to contract when the patient is asked to contract the weak muscle. Weakness may be masked when attempts to contract individual weak muscles are accompanied by activation of other muscles to compensate for the loss of power. In these substitution, or “trick,” movements, the patient exploits a strong muscle with similar function to compensate for the loss of action of a weak muscle. Careful observation for alterations in normal movement patterns and substitution movements may indicate loss of function. Endurance is the ability to perform the same act repeatedly.

The strength examination assesses primarily voluntary, or active, muscle contraction rather than reflex contraction. Strength may be classified as kinetic—the force exerted in changing position—and static—the force exerted in resisting movement from a fixed position. Strength may be tested in two ways. The patient may place a joint in a certain position, and then hold it there as the examiner tries to move it. Alternately the patient may try to move a joint or contract a muscle against the fixed resistance of the examiner. In most disease processes, both are equally affected, and the two methods can be used interchangeably. Some patients may comprehend and cooperate better with the first method, but having the patient initiate movement may better detect mild weakness. There is disagreement about how the examiner should apply force. Some authorities recommend a slow application of resistance in which the patient and examiner match effort; others contend that a rapid movement by the examiner will better detect mild weakness. With very weak muscles, strength may have to be judged without resistance or only against the resistance offered by gravity.


Many factors may complicate the strength examination and make assessment more difficult, such as fatigue, systemic illness, and failure to understand or cooperate with testing. Other conditions may result in a false or distorted impression of weakness, such as extrapyramidal disease, ataxia, impairment of the range of motion due to pain, spasm, joint ankylosis, or contractures, and psychiatric conditions such as hysteria and malingering. Motor impersistence is the inability to sustain voluntary motor acts that have been initiated on verbal command. The patient is unable to sustain an activity, such as keeping the eyes closed or the hand raised. It may be a form of apraxia, and has been said to occur most often with left hemisphere lesions. Passive movements are often helpful to distinguish loss of range of motion due to contractures from other reasons such as weakness, pain, and muscle spasm. With contracture, a muscle cannot be stretched to its normal limits without considerable resistance and the production of pain. Contractures are particularly common in the calf muscles, drawing the foot downward (“tight heel cords”). In evaluating contractures and deformities, it is important to differentiate between those of neurogenic origin and those due to orthopedic disease, congenital abnormalities, habitual postures, occupational factors, or other factors that cause mechanical difficulty with movement.

Strength may be assessed in absolute terms (e.g., the examiner comparing the patient’s power to a belief of what normal should be), or it may be assessed in comparison to the patient’s other muscles. The comparison is most often to a homologous muscle on the other side, as in comparing the two biceps muscles. But proximal strength should be commensurate with distal strength in the same patient. A patient with polymyositis may have weakness of the deltoids on both sides, so one deltoid cannot be judged against the other. But the deltoids may be obviously weaker than the wrist extensors, so there is a proximal to distal gradient of increasing strength that is clearly abnormal. The muscles on the dominant side are usually slightly stronger.

In manual muscle testing (MMT), the strength of individual muscles is tested and graded quantitatively using some scale. Strength is most commonly graded using the 5-level MRC (Medical Research Council) scale, which was developed in Britain in World War II to evaluate patients with peripheral nerve injuries (Table 18.1). The MRC scale has been widely applied to the evaluation of strength in general. However, because of the original purpose the scale is heavily weighted toward the evaluation of very weak muscles. So the most commonly used strength grading scale has significant limitations when dealing with many patients.

There is obviously considerable individual variation in muscle power, affecting examiners as well as patients, dependent in part upon size, gender, body build, age, and activity level. A large, young, powerful physician examining a small, old, sick patient may overcall weakness. Conversely, a small, relatively weak physician examining a large, powerful patient may miss significant weakness because of strength mismatch. As a general principle, reliable strength testing should attempt to break a given muscle. By varying the length of lever and the shortening of the muscle permitted, the examiner may give or take mechanical advantage as necessary to compensate for strength mismatch. Many patients
of different ages, sizes, and strength levels must be examined in this fashion in order to develop an appreciation of the expected strength of a muscle for a given set of circumstances.








TABLE 18.1 The Medical Research Council Scale of Muscle Strength



























0


No contraction


1


A flicker or trace of contraction


2


Active movement with gravity eliminated


3


Active movement against gravity


4−


Active movement against gravity and slight resistance


4


Active movement against gravity and moderate resistance


4+


Active movement against gravity and strong resistance


5


Normal power



PATTERNS OF WEAKNESS

There are common patterns of weakness. Recognition of a pattern may help greatly in lesion localization and differential diagnosis. Identification of the process causing weakness is further aided by accompanying signs, such as reflex alterations and sensory loss. Table 18.2 reviews the features of upper motor neuron vs. lower motor neuron weakness. Table 18.3 summarizes some common patterns of weakness and their localization.

Weakness may be focal or generalized. When focal, it may follow the distribution of some structure in the peripheral nervous system, such as a peripheral nerve or spinal root. It may affect one side of the body in a “hemi” distribution. A hemi distribution may affect the arm, leg, and face equally on one side of the body, or one or more areas may be more involved than others. The corticospinal tract (CST) preferentially innervates certain muscle groups, and these are often selectively impaired. When weakness is nonfocal, it may be generalized, predominantly proximal, or predominantly distal. Identification of the process causing weakness is further aided by accompanying signs, such as reflex alterations and sensory loss.


Generalized Weakness

The term generalized weakness implies that the weakness involves both sides of the body, more or less symmetrically. When a patient has truly generalized weakness, bulbar motor functions—such as facial movements, speech, chewing, and swallowing—are involved as well. Weakness of both arms and both legs with normal bulbar function is quadriparesis or tetraparesis. Weakness of both legs is paraparesis. When weakness affects all four extremities, the likely causes include spinal cord disease, peripheral neuropathy, a neuromuscular junction disorder, or a myopathy.








TABLE 18.2 Features of Upper Motor Neuron vs. Lower Motor Neuron Weakness













































Feature


Upper Motor Neuron


Lower Motor Neuron


Weakness distribution


Corticospinal distribution; hemiparesis, quadriparesis, paraparesis, monoparesis, faciobrachial


Generalized, predominantly proximal, predominantly distal or focal. No preferential involvement of corticospinal innervated muscles


Sensory loss distribution


Central pattern


None, stocking glove or peripheral nerve or root distribution


Deep tendon reflexes


Increased unless very acute


Normal or decreased


Superficial reflexes


Decreased


Normal


Pathological reflexes


Yes


No


Sphincter function


Sometimes impaired


Normal (except for cauda equina lesion)


Muscle tone


Increased


Normal or decreased


Pain


No


Sometimes


Other CNS signs


Possibly


No


CNS, central nervous system.










TABLE 18.3 Common Patterns of Weakness with Lesions at Different Locations in the Neuraxis

































































































Location of Lesion


Distribution of Weakness


Sensory Loss


DTRs**


Possible Accompanying Signs


Middle cerebral artery


Contralateral arm & face > leg*


Y


Incr


Aphasia, apraxia, visual field deficit, gaze palsy


Anterior cerebral


Contralateral leg > arm & face*


Y


Incr


Cortical sensory loss contralateral leg, frontal lobe signs, sometimes incontinence


Internal capsule


Contralateral face = arm = leg*


N


Incr


None (“pure motor stroke”)


Brainstem


Ipsilateral cranial nerve & contralateral body*


Y


Incr


Variable, depending on level


Cervical cord (transverse)


Both arms and both legs*


Y


Incr


Bowel, bladder, or sexual dysfunction common


Thoracic cord (transverse)


Both legs*


Y


Incr


Bowel, bladder, or sexual dysfunction common


Cauda equina


Both legs, asymmetric, multiple root pattern


Y


Decr


Occasional bowel, bladder, or sexual dysfunction; sometimes pain


Anterior horn cell


Focal early, generalized late


N


Incr


Atrophy, fasciculations, bulbar weakness


Single nerve root


Muscles of the affected myotome


Y


Decr


Pain


Plexus


Plexus pattern, complete or partial


Usually


Decr


Pain is common, especially with brachial “plexitis”


Mononeuropathy


Muscles of the affected nerve


Usually


Decr


Variable atrophy, variable pain


Polyneuropathy


Distal > proximal


Usually


Decr


Variable pain, atrophy late


Neuromuscular junction


Bulbar, proximal extremities


N


Normal


Ptosis, ophthalmoparesis, fatigable weakness, fluctuating weakness


Muscle


Proximal > distal


N


Normal


Pain uncommon, many potential patterns (limb girdle, facioscapulohumeral, etc.), pseudohypertrophy, myotonia


DTR, deep tendon reflex; Y, yes; N no; Incr, increased; Decr, decreased.


* Extremity weakness in a corticospinal tract distribution.

** With corticospinal lesions, DTRs acutely may be normal or decreased (neural shock).



When spinal cord disease is the culprit and the deficit is incomplete, more severe involvement of those muscles preferentially innervated by the CST can frequently be discerned. Reflexes are usually increased (though in the acute stages they may be decreased or absent); there is usually some alteration of sensation; sometimes a discrete spinal “level”; superficial reflexes disappear; and there may be bowel and bladder dysfunction. Generalized peripheral nerve disease tends to predominantly involve distal muscles, although there are exceptions. There is no preferential involvement of CST innervated muscles; reflexes are usually decreased; sensory loss is frequently present; and bowel and bladder function are not disturbed. With a neuromuscular junction disorder, the weakness is likely to be worse proximally; sensation is spared; reflexes are normal; and there is usually involvement of bulbar muscles, especially with ptosis and ophthalmoplegia. When the problem is a primary muscle disorder, weakness is usually more severe proximally; reflexes are normal; sensation is normal; and with only a few exceptions, bulbar function is spared except for occasional dysphagia. These are generalizations. Some neuropathies may cause proximal weakness, and some myopathies may affect distal muscles; not all patients with a neuromuscular transmission disorder have bulbar involvement.

Motor neuron disease is a special case. Amyotrophic lateral sclerosis (ALS) characteristically involves both the upper and lower motor neurons. It produces a clinical picture of weakness and wasting due to involvement of the lower motor neurons in the anterior horn of the spinal cord, combined with weakness and hyperreflexia due to involvement of the upper motor neurons in the cerebral cortex that give rise to the corticospinal tract. There is upper motor neuron weakness (cerebral cortex pathology) superimposed on lower motor neuron weakness (spinal cord pathology).


Focal Weakness

Weakness of the arm and leg on one side of the body is hemiparesis. This may range in severity from very mild, manifest only as pronator drift and impairment of fine motor control, to total paralysis. Monoparesis is weakness limited to one extremity, such as the leg contralateral to an anterior cerebral artery stroke. Diplegia is weakness of like parts on the two sides of the body; the term spastic diplegia refers to weakness of both legs that occurs in cerebral palsy; and facial diplegia is weakness of both sides of the face. Spastic weakness of one arm and the opposite leg is referred to as cruciate or crossed paralysis, or hemiplegia alternans. Reflexes—typically increased unless the process is acute—and accompanying sensory loss help identify such focal weakness as central in origin.

Certain patterns of muscle weakness point to a peripheral nerve, plexus, or root lesion. A mononeuropathy, such as a radial nerve palsy, or a spinal root lesion, such as from a herniated disc, causes weakness limited to the distribution of the involved nerve or root. A plexopathy may cause weakness of the entire limb, or weakness only in the distribution of certain plexus components. With such lower motor neuron pathology, reflexes are typically decreased and there is often accompanying sensory loss. Localization of focal weakness due to root, plexus, and peripheral nerve pathology requires intimate familiarity with peripheral neuroanatomy.

With a peripheral nerve lesion, all muscles below the level of the lesion are at risk. When multiple muscles of an extremity are weak in a non-CST distribution, localization depends on recognizing the common innervating structure: root, plexus component, or peripheral nerve.

With lower motor neuron pathology, reflexes are typically decreased, and there is often accompanying sensory loss. Anterior horn cell disease often begins with focal weakness that may simulate mononeuropathy, but it evolves into a more widespread pattern as the disease progresses, culminating in generalized weakness. Except for extraocular muscle involvement in myasthenia gravis, it is rare for a myopathy or neuromuscular junction disorder to cause focal weakness.


NONORGANIC WEAKNESS

The first step in evaluating weakness is often deciding whether it is organic or nonorganic, i.e., due to a psychiatric disorder. This distinction is not always easy. Patients with nonorganic weakness are commonly thought to have neurologic disease, but just as often patients with real weakness are dismissed
as uncooperative, hysterical, or malingering. Coaching is often helpful in improving poor effort, but some patients, in spite of all, will give only erratic and variable effort.

Some things are often useful in distinguishing organic from nonorganic weakness. Patients with bona fide organic muscle weakness will yield smoothly as the examiner defeats the weak muscle. The patient gives uniform resistance throughout the movement. If the examiner decreases his resistance, the patient will begin to win the battle. If the examiner drops the resistance level, the patient with nonorganic weakness will not continue to push or pull. Instead, the patient will also stop resisting so that no matter how little force the examiner applies, there is an absence of follow-through and the patient never overcomes the examiner. When there is nonorganic weakness, resistance is erratic and often collapses abruptly. The muscular contractions are poorly sustained and may give way suddenly, rather than gradually, as the patient resists the force exerted by the examiner. Some patients will give up entirely and allow the muscle or limb to flop; others will provide variable resistance throughout the range of motion with alternating moments of effort and no effort. This pattern of variable strength is referred to as “ratchety,” “give way,” or “catch and give.” It is characteristic of nonorganic weakness. In nonorganic weakness, functional testing may fail to confirm weakness suspected during strength testing. For example, there may be apparent foot dorsiflexion weakness, yet the patient is able to stand on the heel without difficulty. The patient with nonorganic weakness may be calm and indifferent while demonstrating the lack of strength, showing little sign of alarm at the presence of complete paralysis, and smile cheerfully during the examination. If the examiner raises and drops an extremity, a limb with psychogenic paralysis may drop slowly to avoid injury, while an extremity with real weakness would drop rapidly, especially if the paralysis is flaccid.

The Hoover (automatic walking) sign is useful for evaluating suspected nonorganic leg weakness. When a normal supine patient flexes the hip to lift one leg, there is a downward movement of the other leg. The extension counter-movement of the opposite leg is a normal associated movement. An extension movement of one leg normally accompanies flexion of the other leg, as in walking. In organic leg weakness, the downward pressure of the contralateral heel occurs when the patient tries to raise the weak leg, and the examiner can feel the extension pressure by placing a hand beneath the heel that remains on the bed. In nonorganic leg weakness, there is no downward pressure of the contralateral heel, but the extension movement of the “paralyzed” leg may be felt as the good leg is raised (Hoover sign).


EXAMINATION OF MOTOR STRENGTH AND POWER

Reliable strength testing requires proper patient positioning and avoidance of unwanted movements. Testing may be done in various positions depending on the muscle to be tested and its power. Testing in the seated position suffices under most circumstances. It is important to fix the proximal portion of a limb when the movements of the distal portion are being tested. For instance, when testing forearm pronation strength, the patient must not be allowed to internally rotate the shoulder to compensate for lack of pronation power. When evaluating very weak muscles, gravity must be eliminated to detect residual power. A very weak biceps muscle (MRC grade 2/5), even when it cannot succeed against gravity, may be able to flex the elbow if the arm is raised to shoulder height so that the forearm can be moved horizontally. The wrist and finger drop of radial nerve palsy creates such a mechanical disadvantage for contraction that the patient may appear to have weakness of grip and finger abduction, but these functions are intact when the wrist and fingers are passively extended.


EXAMINATION OF SPECIFIC MOVEMENTS AND MUSCLES

Many reference sources are available to assist in learning muscle examination techniques. There is some difference regarding the exact innervation of individual muscles among different reference sources, and occasionally there is variable or anomalous innervation. Table 18.4 through Table 18.7
give the most generally accepted spinal cord segment and peripheral nerve innervation of the more important muscles. Table 18.8 and Table 18.9 give the innervation by root.








TABLE 18.4 Innervation of Muscles Responsible for Movements of the Head and Neck

























































































Muscle


Segmental Innervation


Peripheral Nerve


Sternocleidomastoid


Cranial XI; C (1) 2-3


Spinal accessory nerve


Trapezius


Cranial XI; C (2) 3-4


Spinal accessory nerve


Scalenus anterior


C 4-7


Scalenus medius


C 4-8


Scalenus posterior


C 6-8


Longus capitis


C 1-4


Longus colli


C 2-6


Rectus capitis anterior


C 1-2


Suboccipital nerve


Rectus capitis lateralis


C 1


Suboccipital nerve


Rectus capitis posterior


C 1


Suboccipital nerve


Obliquus capitis inferior


C 1


Suboccipital nerve


Obliquus capitis superior


C 1


Suboccipital nerve


Splenius capitis


C 2-4 (1-6)


Splenius cervicis


C 2-4 (1-6)


Semispinalis capitis


C 1-4


Semispinalis cervicis


C 3-6


Spinalis cervicis


C 5-8


Sacrospinalis


C 1-8


Iliocostalis cervicis


C 1-8


Longissimus capitis


C 1-8


Longissimus cervicis


C 1-8


Intertransversarii


C 1-8


Rotatores


C 1-8


Multifidi


C 1-8



Minor innervation indicated by parentheses.



Examination of Movements and Muscles of the Neck

The principal neck movements are flexion, extension (retraction), rotation (turning), and lateral bending (tilting, abduction). Many different muscle groups contribute to the various neck movements. Except for the sternocleidomastoid (SCM) and trapezius it is not possible to examine them individually, and the assessment is made of movement (e.g., neck flexion) rather than particular muscles. The SCM is a flexor and rotator of the head and neck; the trapezius retracts the neck and
draws it to one side. Other muscles contribute to neck flexion, especially the prevertebral group. Many muscles contribute to neck extension, including the trapezius and the paravertebral muscles. Many of these muscles when contracting unilaterally rotate the spine. The paravertebral musculature is a massive, complex amalgam of individual muscle groups that primarily serve to extend and rotate the neck and trunk.








TABLE 18.5 Innervation of Muscles Responsible for Movements of the Shoulder Girdle and Upper Extremity





























































































































































































































Muscle


Segmental Innervation


Peripheral Nerve


Trapezius


Cranial XI; C (2) 3-4


Spinal accessory nerve


Levator scapulae


C 3-4


Nerves to levator scapulae



C 5


Dorsal scapular nerve


Rhomboideus major


C 4-5


Dorsal scapular nerve


Rhomboideus minor


C 4-5


Dorsal scapular nerve


Serratus anterior


C 5-7


Long thoracic nerve


Deltoid


C 5-6


Axillary nerve


Teres minor


C 5-6


Axillary nerve


Supraspinatus


C (4) 5-6


Suprascapular nerve


Infraspinatus


C (4) 5-6


Suprascapular nerve


Latissimus dorsi


C 6-8


Thoracodorsal nerve


Pectoralis major


C 5-T 1


Lateral and medial anterior thoracic nerves


Pectoralis minor


C 7-T 1


Medial anterior thoracic nerve


Subscapularis


C 5-7


Subscapular nerves


Teres major


C 5-7


Lower subscapular nerve


Subclavius


C 5-6


Nerve to subclavius


Coracobrachialis


C 6-7


Musculocutaneous nerve


Biceps brachii


C 5-6


Musculocutaneous nerve


Brachialis


C 5-6


Musculocutaneous nerve


Brachioradialis


C 5-6


Radial nerve


Triceps brachii


C 6-8


Radial nerve


Anconeus


C 7-8


Radial nerve


Supinator


C 6-7


Radial nerve


Extensor carpi radialis longus


C (5) 6-7


Radial nerve


Extensor carpi radialis brevis


C 7-8


Radial nerve


Extensor carpi ulnaris


C 7-8


Radial nerve


Extensor digitorum communis


C 7-8


Radial nerve


Extensor indicis proprius


C 7-8


Radial nerve


Extensor digiti minimi


C 7-8


Radial nerve


Extensor pollicis longus


C 7-8


Radial nerve


Extensor pollicis brevis


C 7-8


Radial nerve


Abductor pollicis longus


C 7-8


Radial nerve


Pronator teres


C 6-7


Median nerve


Flexor carpi radialis


C 6-7


Median nerve


Pronator quadratus


C 7-8


Median nerve


Palmaris longus


C 7-8


Median nerve


Flexor digitorum superficialis


C 7-T 1


Median nerve


Flexor digitorum profundus (radial half)


C 8-T 1


Median nerve


Lumbricales 1 and 2


C 8-T 1


Median nerve


Flexor pollicis longus


C 7-T 1


Median nerve


Flexor pollicis brevis (lateral head)


C 8-T 1


Median nerve


Abductor pollicis brevis


C 8-T 1


Median nerve


Opponens pollicis


C 8-T 1


Median nerve


Flexor carpi ulnaris


C 7-T 1


Ulnar nerve


Flexor digitorum profundus (ulnar half)


C 8-T 1


Ulnar nerve


Interossei


C 8-T 1


Ulnar nerve


Lumbricales 3 and 4


C 8-T 1


Ulnar nerve


Flexor pollicis brevis (medial head)


C 8-T 1


Ulnar nerve


Flexor digiti minimi brevis


C 8-T 1


Ulnar nerve


Abductor digiti minimi


C 8-T 1


Ulnar nerve


Opponens digiti minimi


C 8-T 1


Ulnar nerve


Palmaris brevis


C 8-T 1


Ulnar nerve


Adductor pollicis


C 8-T 1


Ulnar nerve


Minor innervation indicated by parentheses.



Neck flexors are tested by having the patient try to place the chin on the chest as the examiner applies extension force to the forehead (Figure 18.1). Extensors are tested by having the patient extend against the examiner’s resistance applied to the occiput (Figure 18.2). Neck rotation is accomplished by the contralateral SCM and ipsilateral splenius capitus and trapezius; examination of the SCM and trapezius muscles is discussed in Chapter 15. Neck flexor strength may be tested with the patient sitting or supine, neck extension sitting or prone. Examination of the neck muscles must be done carefully in any patient at risk for cervical spine disease.









TABLE 18.6 Innervation of Muscles Responsible for Movements of the Thorax and Abdomen



















































Muscle


Segmental Innervation


Peripheral Nerve


Diaphragm


C 3-5


Phrenic nerve


Intercostal muscles (internal and external)


T 1-12


Intercostal nerves


Levatores costarum


C 8-T 11


Intercostal nerves


Transversus thoracis


T 2-7


Intercostal nerves


Serratus posterior superior


T 1-4


Intercostal nerves


Serratus posterior inferior


T 9-12


Intercostal nerves


Rectus abdominis


T 5-12


Intercostal nerves


Pyramidalis


T 11-12


Intercostal nerves


Transversus abdominis


T 7-L 1


Intercostal, ilioinguinal, and iliohypogastric nerves


Obliquus internus abdominis


T 7-L 1


Intercostal, ilioinguinal, and iliohypogastric nerves


Obliquus externus abdominis


T 7-L 1


Intercostal, ilioinguinal, and iliohypogastric nerves










TABLE 18.7 Innervation of Muscles Responsible for Movements of the Lower Extremities

















































































































































































































Muscle


Segmental Innervation


Peripheral Nerve


Psoas major


L (1) 2-3 (4)


Nerve to psoas major


Psoas minor


L 1-2


Nerve to psoas minor


lliacus


L 2-3 (4)


Femoral nerve


Quadriceps femoris


L 2-4


Femoral nerve


Sartorius


L 2-3


Femoral nerve


Pectineus


L 2-3


Femoral nerve


Gluteus maximus


L 5-S 2


Inferior gluteal nerve


Gluteus medius


L 4-S 1


Superior gluteal nerve


Gluteus minimus


L 4-S 1


Superior gluteal nerve


Tensor fasciae latae


L 4-S 1


Superior gluteal nerve


Piriformis


(L5) S 1-2


Nerve to piriformis


Adductor longus


L 2-4


Obturator nerve


Adductor brevis


L 2-4


Obturator nerve


Adductor magnus


L 2-4


Obturator nerve


Adductor magnus


L 4-5


Sciatic nerve


Gracilis


L 2-4


Obturator nerve


Obturator externus


L 2-4


Obturator nerve


Obturator internus


L 5-S 1


Nerve to obturator internus


Gemellus superior


L 5-S 1


Nerve to obturator internus


Gemellus inferior


L 5-S 1


Nerve to quadratus femoris


Quadratus femoris


L 5-S 1


Nerve to quadratus femoris


Biceps femoris (long head)


L 5-S 1


Tibial nerve


Semimembranosus


L 5-S 1


Tibial nerve


Semitendinosus


L 5-S 2


Tibial nerve


Popliteus


L 5-S 1


Tibial nerve


Gastrocnemius


S 1-S 2


Tibial nerve


Soleus


S 1-S 2


Tibial nerve


Plantaris


S 1-S 2


Tibial nerve


Tibialis posterior


L 5-S 1


Tibial nerve


Flexor digitorum longus


L 5-S 1


Tibial nerve


Flexor hallucis longus


L 5-S 1


Tibial nerve


Biceps femoris (short head)


L 5-S 2


Common peroneal nerve


Tibialis anterior


L 4-L 5


Deep peroneal nerve


Peroneus tertius


L 5-S 1


Deep peroneal nerve


Extensor digitorum longus


L 5-S 1


Deep peroneal nerve


Extensor hallucis longus


L 5


Deep peroneal nerve


Extensor digitorum brevis


L 5-S 1


Deep peroneal nerve


Extensor hallucis brevis


L 5-S 1


Deep peroneal nerve


Peroneus longus


L 5-S 1


Superficial peroneal nerve


Peroneus brevis


L 5-S 1


Superficial peroneal nerve


Flexor digitorum brevis


S 1-2


Medial plantar nerve


Flexor hallucis brevis


S 1-2


Medial plantar nerve


Abductor hallucis


S 1-2


Medial plantar nerve


Lumbricales (medial 1 or 2)


S 1-3


Medial plantar nerve


Quadratus plantae


S 1-2


Lateral plantar nerve


Adductor hallucis


S 2-3


Lateral plantar nerve


Abductor digiti minimi pedis


S 1-3


Lateral plantar nerve


Flexor digiti minimi brevis


S 2-3


Lateral plantar nerve


Lumbricales (lateral 2 or 3)


S 1-3


Lateral plantar nerve


Interossei


S 2-3


Lateral plantar nerve


Minor innervation indicated by parentheses.

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Jun 19, 2016 | Posted by in NEUROLOGY | Comments Off on Motor Strength and Power

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