COMMENTARY

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Use of the Medical Research CouncilMuscle Strength Grading System in the

Upper ExtremityMichelle A. James, MD

From Shriners Hospital for Children Northern California and University of California Davis School of

Medicine, Sacramento, CA.

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istory of Muscle Strength Gradinghe Medical Research Council of Great Britain

MRC) system is the best known and most com-only used muscle strength grading system for man-

al muscle testing (MMT) worldwide. Dyck et al1

race the development of the MRC system to thereatment of war injuries and poliomyelitis. S.W.

itchell, a Civil War surgeon, recognized nerveamage as a cause of muscle weakness in 1872.itchell and M.J. Lewis were later responsible for

he first known effort to grade neuromuscular signshen they classified ataxic gait in 1886. In 1917,.W. Lovett, a Boston orthopedist, published theuscle scoring system later adapted by the MRC

ased on his experience treating poliomyelitis; heredited W. Wright, a physical therapist, with devel-ping the muscle testing methods.2 As a result ofheir experiences treating World War II injuries, 12urgeons formed the Nerve Injuries Committee of theritish Army (G. Riddoch [Chair], W.R. Bristow,.W.B. Cairns, E.A. Carmichael, M. Critchley, J.G.reenfield, J.R. Learmonth, H. Platt, H.J. Seddon,.P. Symonds, J.Z. Young, F.J.C. Herrald) and de-eloped the classic handbook Aids to the Investiga-ion of Peripheral Nerve Injuries.3 This manual il-ustrates the major actions of limb muscles and howhey should be tested; defines the concepts of primeovers, synergists, and antagonists; and includes theuscle grading scale familiar to all orthopedic sur-

eons (Table 1). A modified version of this manual,ids to the Examination of the Peripheral Nervousystem, fourth edition, was published in 2000.4 Be-ause the MRC system was intended to be used torade recovery from paralysis (grade 0) attributableo nerve repair, the greatest emphasis is placed onevere degrees of weakness (grades 1, 2, 3); althoughhis system is ordinal, the difference in strength be-ween different grades was not assumed to be con-

tant. In general, the intertester and intratester reli- g

54 The Journal of Hand Surgery

bility of MMT graded with the MRC system hasroven acceptable.2

roblems With the MRCot surprisingly, the MRC system has been widelysed to describe muscle strength in the upper ex-remities of people with conditions other than warnjuries and poliomyelitis. It has been modifiedlmost as often as it has been used, primarilyecause of the wide, difficult-to-quantify gaps be-ween grades 3 and 4 and grades 4 and 5 andecause large joint motors such as the deltoid mayecover enough strength to provide resistance to

MT (grade 4) without having enough strength ortrong enough synergists to provide full motiongainst gravity (grade 3). Another problem withhis system is inherent intersubject variability inuscle strength, rendering it useful primarily for

ntrasubject changes in strength rather than inter-ubject comparisons. In addition, this systemempts the examiner to consider a muscle with aertain grade of strength as having the same degreef recovery as another muscle with the same grade,hen in fact the amount of recovery necessary to

nable the deltoid to be graded 3 may be consid-rably different than the amount of recovery nec-ssary to enable a wrist extensor to be graded 3.he challenges of applying MMT graded by theRC to all types of nerve injuries as a measure-ent of the results of modern repair techniques,

ombined with the fact that no other muscle grad-ng scales are widely accepted, have led to at-empts to modify this system. “Critical Reappraisalf MRC Muscle Testing for Elbow Flexion” byacAvoy and Green quantifies some of the prob-

ems encountered when the MRC is used otherhan as originally intended—for instance, to quan-ify improvement between grades, especially

rades 3, 4, and 5.

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Michelle A. James / MRC Grading in the Upper Extremity 155

odifications of the MRCn the past 6 years at least 8 publications in Theournal of Hand Surgery have referred to this grad-ng system to quantify the results of surgical recon-truction in tetraplegia,5 nerve repair,6 brachiallexus birth palsy,7–9 brachial plexus injury,10,11 andpposition transfer for carpal tunnel syndrome.12 Allited the MRC (although Leechavengvongs et al10,11

id not cite an original MRC publication), but allodified its intended use by presenting only preop-

rative data5,8; reporting only “average increase ofritish Medical Research Council units”12; subdivid-

ng grade 4 into 4–, 4, and 4�5; adding together thecores of muscles sharing the innervation of a pe-ipheral nerve to create a composite score6; describ-ng deltoid function as grade 4 without full shoulderbduction against gravity9,11; or eliminating grades 4nd 5 but expanding grades 2 and 3.7 Of all theseecent Journal of Hand Surgery publications, onlyhen et al9 and Curtis et al7 note that they have usedmodified version of the MRC, and only Curtis et al7

ormally validated their modification, the Activeovement Scale, by studying interrater reliability.

iscussionerhaps World War II surgeons using early tech-iques of nerve repair were gratified to achieve gradestrength in a previously paralyzed muscle, and the

ifferences between grades 3, 4, and 5 did not con-ern them, because this level of recovery was usuallyot attained. Modern techniques may achieve betteresults and engender higher expectations of a mea-urement system.

A new system of grading for MMT should retainhe advantages of the MRC (wide acceptability, easef use, usefulness for most muscles, applicability tootor recovery from all types of nerve injury). Use-

ul potential modifications of the MRC include a

Table 1. Medical Research Council Grades

Grade Muscle State

0 No contraction1 Flicker or trace of contraction2 Active movement with gravity

eliminated3 Active movement against gravity4 Active movement against gravity

and resistance5 Normal power

Data from the Medical Research Council.3

rade for a muscle that achieves strength against

esistance but not against gravity and a standardizedubdivision of grade 4.

At the cost of the convenience of MMT, actualeasurement of torque provides much more detailed

nd accurate measurement of muscle strength, espe-ially for the shoulder and elbow.13–16 The gold stan-ard is isokinetic dynamometry using machinery (eg,ybex [Medway, MA], KinCom [IsoKinetic Interna-

ional, Harrison, TN]). The clinical usefulness of such aachine, however, is limited by the cost and size of the

pparatus and the time required for positioning andesting.15 In addition, the minimum measurable strengthn some isokinetic dynamometers may be more thanhat recoverable by nerve repair. Specialized devicesave been developed for measuring isometric elbownd shoulder strength13,14 and hand and wrist twistingtrength,17 but these are not widely available. A hand-eld dynamometer (HHD) provides more accurateeasurements of isometric muscle strength than MMT

nd is easy to use as long as the examiner has sufficienttrength to stabilize the device.15,16 Methods of increas-ng reproducibility and reliability using a HHD haveeen developed, and normative data are available forifferent populations.16 (An example of such a devicevailable in the United States is the microFET 2 Dyna-ometer; Hoggan Health Industries [West Jordan, UT]).Unless HHD is widely adopted or until a better

rading system is developed and well validated, theRC will continue to be used. When it is altered,

hese alterations should be specifically described andnumerated, and the resulting system should be re-erred to as a modification. Otherwise, tinkering withhe MRC erodes the elegant and prescient intent ofhe Nerve Injuries Committee. With their publicationf the MRC, this group of surgeons accomplished aemarkable achievement: a simple grading systemsed worldwide for over 60 years, applied with ex-raordinary success despite its shortcomings. Its widecceptance precludes the need for further validation ofhe MRC, but any substantial alterations should bealidated before presentation to show that they reliablynd reproducibly achieve the goals of the investigators.

eceived for publication November 13, 2006; accepted in revised formovember 15, 2006.No benefits in any form have been received or will be received fromcommercial party related directly or indirectly to the subject of this

rticle.Corresponding author: Michelle A. James, MD, Shriners Hospital for

hildren, 2425 Stockton Blvd, Sacramento CA 95817; e-mail:james@shrinenet.org.Copyright © 2007 by the American Society for Surgery of the Hand0363-5023/07/32A02-0002$32.00/0

doi:10.1016/j.jhsa.2006.11.008

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156 The Journal of Hand Surgery / Vol. 32A No. 2 February 2007

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3. Medical Research Council. Aids to the investigation of pe-ripheral nerve injuries. 2nd ed. London: Her Majesty’s Sta-tionery Office, 1943.

4. Aids to the examination of the peripheral nervous system.4th ed. London: Elsevier Saunders, 2000.

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7. Miller MC, Nair M, Baratz ME. A device for assessment ofhand and wrist coronal plane strength. J Biomech Eng 2005;

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