Chapter 14Chapter 14

The Shoulder ComplexThe Shoulder Complex

OverviewOverview

The shoulder is a complex set of The shoulder is a complex set of articulations that work together articulations that work together toward the common goal of toward the common goal of positioning the hand in space, positioning the hand in space, which allows an individual to which allows an individual to interact with the environment and interact with the environment and to perform fine motor functionsto perform fine motor functions

AnatomyAnatomy

Although the entire shoulder complex Although the entire shoulder complex functions as an integrated unit, it is functions as an integrated unit, it is anatomically simpler to describe each joint anatomically simpler to describe each joint separately. The shoulder joint complex separately. The shoulder joint complex consists of:consists of:– Three bones (the humerus, the clavicle, and Three bones (the humerus, the clavicle, and

the scapula)the scapula) – Three joints (the sternoclavicular (S-C), the Three joints (the sternoclavicular (S-C), the

acromioclavicular (A-C), and the glenohumeral acromioclavicular (A-C), and the glenohumeral (G-H) joints)(G-H) joints)

– One “pseudojoint” One “pseudojoint” – One physiological area One physiological area

AnatomyAnatomy

Glenohumeral JointGlenohumeral Joint– The glenohumeral (G-H) joint is a The glenohumeral (G-H) joint is a

true synovial-lined diathrodial joint true synovial-lined diathrodial joint that connects the upper extremity to that connects the upper extremity to the trunk, as part of a kinetic chainthe trunk, as part of a kinetic chain

– The GH joint is formed by the The GH joint is formed by the humeral head and the glenoid fossa humeral head and the glenoid fossa of the scapulaof the scapula

AnatomyAnatomy

Glenoid fossaGlenoid fossa– The glenoid fossa is flat, but is made The glenoid fossa is flat, but is made

approximately 50% deeper and approximately 50% deeper and more concave by a ring of more concave by a ring of fibrocartilage called a labrumfibrocartilage called a labrum

– The labrum, which forms part of the The labrum, which forms part of the articular surface, is attached to the articular surface, is attached to the margin of the glenoid cavity and the margin of the glenoid cavity and the joint capsule, and contributes to joint capsule, and contributes to joint stability joint stability

AnatomyAnatomy

ScapulaScapula– The scapula forms the base of the G-H jointThe scapula forms the base of the G-H joint– It is a flat blade of bone that lies along the It is a flat blade of bone that lies along the

thoracic cage at 30° to the frontal plane, 3° thoracic cage at 30° to the frontal plane, 3° superiorly relative to the transverse plane, superiorly relative to the transverse plane, and 20° forward in the sagittal planeand 20° forward in the sagittal plane

– The scapula’s wide and thin configuration The scapula’s wide and thin configuration allows for its smooth gliding along the allows for its smooth gliding along the thoracic wall, and provides a large surface thoracic wall, and provides a large surface area for muscle attachments both distally area for muscle attachments both distally and proximallyand proximally

AnatomyAnatomy

ScapulaScapula– A prominent feature of the scapula in man is A prominent feature of the scapula in man is

the large overhanging acromion, which, along the large overhanging acromion, which, along with the coracoacromial ligament functionally with the coracoacromial ligament functionally enlarges the glenohumeral socketenlarges the glenohumeral socket

– The position of the acromion also places the The position of the acromion also places the deltoid muscle in a dominant position to deltoid muscle in a dominant position to provide strength during elevation of the armprovide strength during elevation of the arm

– Although the acromion appears to be flat, three Although the acromion appears to be flat, three types of acromion morphology have been types of acromion morphology have been described, of which the hooked is associated described, of which the hooked is associated with an increase in rotator cuff pathology with an increase in rotator cuff pathology

AnatomyAnatomy

Joint capsuleJoint capsule– The voluminous joint capsule of the The voluminous joint capsule of the

glenohumeral joint allows for large amounts of glenohumeral joint allows for large amounts of motion to occur at the G-H jointmotion to occur at the G-H joint

– The lateral attachment of the glenohumeral The lateral attachment of the glenohumeral joint capsule attaches to the anatomical neck.joint capsule attaches to the anatomical neck.

– Medially, the capsule is attached to the Medially, the capsule is attached to the periphery of the glenoid and its labrumperiphery of the glenoid and its labrum

– The overall strength of the joint capsule bears The overall strength of the joint capsule bears an inverse relationship to the patient’s age: the an inverse relationship to the patient’s age: the older the patient, the weaker the joint capsuleolder the patient, the weaker the joint capsule

AnatomyAnatomy

The greater and lesser tuberositiesThe greater and lesser tuberosities– Located on the lateral aspect of the anatomical neck Located on the lateral aspect of the anatomical neck

of the humerusof the humerus– Serve as attachment sites for the tendons of the Serve as attachment sites for the tendons of the

rotator cuff musclesrotator cuff muscles– The greater tuberosity serves as the attachment for The greater tuberosity serves as the attachment for

the supraspinatus, infraspinatus and teres minor the supraspinatus, infraspinatus and teres minor – The lesser tuberosity serves as the attachment for The lesser tuberosity serves as the attachment for

the subscapularisthe subscapularis– The greater and lesser tuberosities are separated by The greater and lesser tuberosities are separated by

the intertubercular groove, through which passes the the intertubercular groove, through which passes the tendon of the long head of the biceps on its route to tendon of the long head of the biceps on its route to attach on the superior rim of the glenoid fossaattach on the superior rim of the glenoid fossa

AnatomyAnatomy

The glenohumeral ligaments The glenohumeral ligaments – At the anterior portion of the outer fibers of At the anterior portion of the outer fibers of

the joint capsule, three local reinforcements the joint capsule, three local reinforcements are present: the superior, middle and are present: the superior, middle and inferior G-H ligaments (inferior G-H ligaments (>>ZZ== ligaments) ligaments)

Superior - serves to limit external rotation and Superior - serves to limit external rotation and inferior translation of the humeral head with the inferior translation of the humeral head with the arm at the sidearm at the side

Middle - serves to limit external rotation (Table Middle - serves to limit external rotation (Table 14-5) and anterior translation of the humeral head 14-5) and anterior translation of the humeral head with the arm in 0° and 45° of abduction with the arm in 0° and 45° of abduction

Inferior - consists of an anterior band, a posterior Inferior - consists of an anterior band, a posterior band, and an axillary pouch with varying functionsband, and an axillary pouch with varying functions

AnatomyAnatomy

The coracohumeral ligamentThe coracohumeral ligament– Covers the superior G-H ligament Covers the superior G-H ligament

anterior-superiorly, and fills the anterior-superiorly, and fills the space between the tendons of the space between the tendons of the supraspinatus and subscapularis supraspinatus and subscapularis muscle; uniting these tendons to muscle; uniting these tendons to complete the rotator cuff in this areacomplete the rotator cuff in this area

AnatomyAnatomy

The coracoacromial ligamentThe coracoacromial ligament– Consists of two bands that join near Consists of two bands that join near

the acromion and is ideally suited, the acromion and is ideally suited, both anatomically and both anatomically and morphologically, to prevent morphologically, to prevent separation of the A-C joint surfacesseparation of the A-C joint surfaces

AnatomyAnatomy

Coracoacromial ArchCoracoacromial Arch– Formed by the anterior-inferior aspect of the Formed by the anterior-inferior aspect of the

acromion process, coracoacromial ligament, acromion process, coracoacromial ligament, and inferior surface of the A-C jointand inferior surface of the A-C joint

During overhead motion in the plane of the During overhead motion in the plane of the scapula, the supraspinatus tendon, the region of scapula, the supraspinatus tendon, the region of the cuff most involved in the degenerative the cuff most involved in the degenerative process, can pass directly underneath the process, can pass directly underneath the coracoacromial archcoracoacromial arch

If the arm is elevated while internally rotated, the If the arm is elevated while internally rotated, the supraspinatus tendon passes under the supraspinatus tendon passes under the coracoacromial ligament, whereas if the arm is coracoacromial ligament, whereas if the arm is externally rotated, the tendon passes under the externally rotated, the tendon passes under the acromion itselfacromion itself

AnatomyAnatomy

Suprahumeral/subacromial spaceSuprahumeral/subacromial space– An area located on the superior An area located on the superior

aspect of the G-H jointaspect of the G-H joint– Contents include the long head of Contents include the long head of

biceps tendon, supraspinatus and biceps tendon, supraspinatus and upper margins of subscapularis and upper margins of subscapularis and infraspinatus, subdeltoid-infraspinatus, subdeltoid-subacromial bursa subacromial bursa

– The space is at its narrowest The space is at its narrowest between 60° and 120° of scaption between 60° and 120° of scaption

AnatomyAnatomy

The subacromial bursaThe subacromial bursa– One of the largest bursa in the bodyOne of the largest bursa in the body– Provides two smooth serosal layers; Provides two smooth serosal layers;

one of which adheres to the one of which adheres to the overlying deltoid muscle and the overlying deltoid muscle and the other to the rotator cuff lying other to the rotator cuff lying beneathbeneath

AnatomyAnatomy

NeurologyNeurology– The shoulder complex is The shoulder complex is

embryologically derived from C 5-8, embryologically derived from C 5-8, except the A-C joint, which is except the A-C joint, which is derived from C 4. The sympathetic derived from C 4. The sympathetic nerve supply to the shoulder nerve supply to the shoulder originates primarily in the thoracic originates primarily in the thoracic region from T 2 down as far as T 8region from T 2 down as far as T 8

AnatomyAnatomy

VascularizationVascularization– The vascular supply to the rotator The vascular supply to the rotator

cuff muscles of the shoulder consists cuff muscles of the shoulder consists of three main sources: the of three main sources: the thoracoacromial, suprahumeral, and thoracoacromial, suprahumeral, and subscapular arteriessubscapular arteries

– The brachial artery provides the The brachial artery provides the dominant arterial supply to each of dominant arterial supply to each of the two heads of the bicepsthe two heads of the biceps

AnatomyAnatomy

Glenohumeral jointGlenohumeral joint– Close packed positionClose packed position

The close packed position for the G-H joint is 90The close packed position for the G-H joint is 90 of glenohumeral abduction and full external of glenohumeral abduction and full external rotation; or full abduction and external rotation, rotation; or full abduction and external rotation, depending on the sourcedepending on the source

– Open packed positionOpen packed position Without internal or external rotation occurring, Without internal or external rotation occurring,

the open packed, or rest position of the G-H the open packed, or rest position of the G-H joint has traditionally been cited as 55° of semi-joint has traditionally been cited as 55° of semi-abduction and 30° of horizontal adductionabduction and 30° of horizontal adduction

AnatomyAnatomy

Glenohumeral jointGlenohumeral joint– Capsular patternCapsular pattern

According to Cyriax, the capsular According to Cyriax, the capsular pattern for the shoulder is external pattern for the shoulder is external rotation the most limited, abduction the rotation the most limited, abduction the next most limited, and internal rotation next most limited, and internal rotation the least limited in a 3:2:1 ratio the least limited in a 3:2:1 ratio respectively respectively

AnatomyAnatomy

The acromioclavicular jointThe acromioclavicular joint – The acromioclavicular (A-C) joint is a The acromioclavicular (A-C) joint is a

diarthrodial joint, formed by the diarthrodial joint, formed by the acromion and the lateral end of the acromion and the lateral end of the clavicleclavicle

– The joint serves as the main articulation The joint serves as the main articulation suspending the upper extremity from suspending the upper extremity from the trunk, and it is at this joint about the trunk, and it is at this joint about which the scapular moveswhich the scapular moves

AnatomyAnatomy

Acromioclavicular jointAcromioclavicular joint– The articulating surface of the lateral The articulating surface of the lateral

end of the clavicle can be either end of the clavicle can be either convex or concave and corresponds convex or concave and corresponds with the articulating surface of the with the articulating surface of the acromion. Consequently, although the acromion. Consequently, although the joint is described as a planar joint, joint is described as a planar joint, there is often a male-female there is often a male-female relationship, with 3 degrees of freedomrelationship, with 3 degrees of freedom

AnatomyAnatomy

A-C ligamentsA-C ligaments– The coracoclavicular ligaments The coracoclavicular ligaments

(conoid and trapezoid) are the (conoid and trapezoid) are the primary support for the A-C jointprimary support for the A-C joint

– These ligaments provide mainly These ligaments provide mainly vertical stability, with control of vertical stability, with control of superior and anterior translation as superior and anterior translation as well as anterior axial rotation well as anterior axial rotation

AnatomyAnatomy

A-C jointA-C joint– Neurology.Neurology. Innervation to this joint Innervation to this joint

is provided by the suprascapular, is provided by the suprascapular, lateral pectoral, and axillary nerveslateral pectoral, and axillary nerves

– Capsular pattern. Lacks a true Capsular pattern. Lacks a true capsular patterncapsular pattern

– Close and open packed positions. Close and open packed positions. UndeterminedUndetermined

AnatomyAnatomy

Sternoclavicular (S-C) jointSternoclavicular (S-C) joint– Represents the articulation between the Represents the articulation between the

medial end of the clavicle, the clavicular medial end of the clavicle, the clavicular notch of the manubrium of the sternum, notch of the manubrium of the sternum, and the cartilage of the first rib, which and the cartilage of the first rib, which forms the floor of the jointforms the floor of the joint

– Has been classified as a ball and socket Has been classified as a ball and socket joint, a plane joint, and as a saddle jointjoint, a plane joint, and as a saddle joint

– A meniscus completely divides the joint A meniscus completely divides the joint into two cavitiesinto two cavities

AnatomyAnatomy

Sternoclavicular (S-C) jointSternoclavicular (S-C) joint– Ligaments. A number of ligaments Ligaments. A number of ligaments

provide support to this joint:provide support to this joint: Anterior sternoclavicular ligamentAnterior sternoclavicular ligament Posterior sternoclavicular ligamentPosterior sternoclavicular ligament InterclavicularInterclavicular Costoclavicular Costoclavicular

AnatomyAnatomy

Sternoclavicular (S-C) jointSternoclavicular (S-C) joint– Close packed positionClose packed position. . The close packed The close packed

position for the S-C joint is maximum arm position for the S-C joint is maximum arm elevation and protractionelevation and protraction

– Open packed position. The open packed Open packed position. The open packed position for the S-C joint has yet to be position for the S-C joint has yet to be determined, but is likely to be when the determined, but is likely to be when the arm is by the sidearm is by the side

– Capsular pattern. Lacks a specific capsular Capsular pattern. Lacks a specific capsular pattern pattern

AnatomyAnatomy

Scapulothoracic JointScapulothoracic Joint – Functionally a joint but it lacks the Functionally a joint but it lacks the

anatomic characteristics of a true anatomic characteristics of a true synovial jointsynovial joint

– Plays a significant role in all motions Plays a significant role in all motions of the shoulder complex of the shoulder complex

AnatomyAnatomy

Muscles of the Shoulder ComplexMuscles of the Shoulder Complex– For simplicity, the muscles acting at For simplicity, the muscles acting at

the shoulder may be described in the shoulder may be described in terms of their functional roles: terms of their functional roles: scapular pivoters, humeral scapular pivoters, humeral propellers, humeral positioners, and propellers, humeral positioners, and shoulder protectorsshoulder protectors

AnatomyAnatomy

Muscles of the Shoulder ComplexMuscles of the Shoulder Complex– Scapular pivotersScapular pivoters

Comprise the trapezius, serratus Comprise the trapezius, serratus anterior, levator scapulae, rhomboid anterior, levator scapulae, rhomboid major, and rhomboid minormajor, and rhomboid minor

As a group, these muscles are involved As a group, these muscles are involved with motions at the scapulothoracic with motions at the scapulothoracic articulation, and their proper function is articulation, and their proper function is vital to the normal biomechanics of the vital to the normal biomechanics of the whole shoulder complex whole shoulder complex

AnatomyAnatomy

Muscles of the Shoulder ComplexMuscles of the Shoulder Complex– Humeral propellersHumeral propellers

Comprise the latissimus dorsi, pectoralis Comprise the latissimus dorsi, pectoralis major, and pectoralis minormajor, and pectoralis minor

AnatomyAnatomy

Muscles of the Shoulder ComplexMuscles of the Shoulder Complex– Humeral positioners. Comprised of Humeral positioners. Comprised of

the three parts of the deltoid musclethe three parts of the deltoid muscle

AnatomyAnatomy

Muscles of the Shoulder ComplexMuscles of the Shoulder Complex– Shoulder protectorsShoulder protectors

Rotator cuffRotator cuff Biceps brachiiBiceps brachii

BiomechanicsBiomechanics

Complete movement at the shoulder girdle Complete movement at the shoulder girdle involves a complex interaction between involves a complex interaction between the glenohumeral, acromioclavicular, the glenohumeral, acromioclavicular, sternoclavicular, scapulothoracic, upper sternoclavicular, scapulothoracic, upper thoracic, costal and sternomanubrial joints, thoracic, costal and sternomanubrial joints, and the lower cervical spineand the lower cervical spine

During these motions, the scapula During these motions, the scapula invariably acts as a platform upon which invariably acts as a platform upon which shoulder rotation and arm activities are shoulder rotation and arm activities are basedbased

BiomechanicsBiomechanics

The Scapulohumeral RhythmThe Scapulohumeral Rhythm – The combination and synchronization of the The combination and synchronization of the

motions that occur between the scapula and motions that occur between the scapula and the humerus during arm elevationthe humerus during arm elevation

– An early study by Inman determined that a An early study by Inman determined that a 2:1 ratio existed between the motion 2:1 ratio existed between the motion occurring at the G-H joint and scapula occurring at the G-H joint and scapula respectivelyrespectively

– This ratio is not consistent throughout the This ratio is not consistent throughout the range of motion range of motion

BiomechanicsBiomechanics

Force couplesForce couples– During the first 30° of upward rotation of During the first 30° of upward rotation of

the scapula, the serratus anterior muscle the scapula, the serratus anterior muscle and the upper and lower divisions of the and the upper and lower divisions of the trapezius muscle are considered the trapezius muscle are considered the principal upward rotators of the scapulaprincipal upward rotators of the scapula

Together these muscles form two force couples; Together these muscles form two force couples; one formed by the upper trapezius, and the one formed by the upper trapezius, and the upper serratus anterior muscles, the other upper serratus anterior muscles, the other formed by the lower trapezius, and lower formed by the lower trapezius, and lower serratus anterior musclesserratus anterior muscles

ExaminationExamination

In the presence of shoulder girdle In the presence of shoulder girdle dysfunction (assuming systemic or dysfunction (assuming systemic or orthopedic causes have been ruled out), orthopedic causes have been ruled out), there are three possible causes for there are three possible causes for shoulder girdle dysfunctionshoulder girdle dysfunction– Compromise of the passive restraint Compromise of the passive restraint

components of the shoulder girdle components of the shoulder girdle – Compromise of the neuromuscular system’s Compromise of the neuromuscular system’s

production or control of shoulder girdle motion production or control of shoulder girdle motion – Compromise to one or more of the of the Compromise to one or more of the of the

neighboring joints that contribute to shoulder neighboring joints that contribute to shoulder girdlegirdle

ExaminationExamination

HistoryHistory– A good history is the cornerstone of proper A good history is the cornerstone of proper

diagnosis, especially since shoulder pain has a diagnosis, especially since shoulder pain has a broad spectrum of patterns and characteristicsbroad spectrum of patterns and characteristics

– It is important to establish the patient’s chief It is important to establish the patient’s chief presenting complaint (which is not always presenting complaint (which is not always pain) as well as defining their other symptoms. pain) as well as defining their other symptoms. The most common complaints associated with The most common complaints associated with shoulder pathology include pain, instability, shoulder pathology include pain, instability, stiffness, deformity, locking, and swelling stiffness, deformity, locking, and swelling

ExaminationExamination

Systems reviewSystems review– Symptoms that are not associated Symptoms that are not associated

with movement should alert the with movement should alert the clinician to a more serious conditionclinician to a more serious condition

– Scenarios related to the shoulder Scenarios related to the shoulder that warrant further investigation by that warrant further investigation by the clinician include an insidious the clinician include an insidious onset of symptoms, and complaints onset of symptoms, and complaints of numbness or paresthesia in the of numbness or paresthesia in the upper extremityupper extremity

ExaminationExamination

ObservationObservation– The clinician observes how the patient The clinician observes how the patient

holds the arm, the overall position of the holds the arm, the overall position of the upper extremity, and the willingness of the upper extremity, and the willingness of the patient to move the armpatient to move the arm

– Deformity is a common complaint with Deformity is a common complaint with injuries of the A-C joint and fractures of injuries of the A-C joint and fractures of the claviclethe clavicle

– A number of static tests for the scapular A number of static tests for the scapular position existposition exist

ExaminationExamination

PalpationPalpation– The optimal methods of palpating the The optimal methods of palpating the

shoulder tendons occur in regions where shoulder tendons occur in regions where there is the least amount of overlying soft there is the least amount of overlying soft tissuetissue

– It is best to divide the shoulder complex into It is best to divide the shoulder complex into compartments for palpationcompartments for palpation

– Symptoms reproduced by palpation in these Symptoms reproduced by palpation in these compartments are frequently associated compartments are frequently associated with a specific underlying pathologywith a specific underlying pathology

ExaminationExamination

AROM, PROM with overpressureAROM, PROM with overpressure– McClure and Flowers classify limited shoulder McClure and Flowers classify limited shoulder

motion into two categories: motion into two categories: Decreased ROM secondary to changes in the Decreased ROM secondary to changes in the

periarticular structures, including shortening of the periarticular structures, including shortening of the capsule, ligaments, or muscles as well as adhesion capsule, ligaments, or muscles as well as adhesion formation. Clinical findings for this category include a formation. Clinical findings for this category include a history of trauma, immobilization, presence of a history of trauma, immobilization, presence of a capsular pattern, capsular end-feel, and no pain with capsular pattern, capsular end-feel, and no pain with the isometric testingthe isometric testing

Decreased ROM due to nonstructural problems, Decreased ROM due to nonstructural problems, including the presence of pain, protective muscle including the presence of pain, protective muscle spasm, or a loose body within the joint space. Clinical spasm, or a loose body within the joint space. Clinical findings for this patient include a history of trauma or findings for this patient include a history of trauma or overuse, and the presence of a non-capsular pattern overuse, and the presence of a non-capsular pattern

ExaminationExamination

Examination of the Dynamic Examination of the Dynamic ScapulaScapula– Given the importance of the Given the importance of the

scapulothoracic joint to overall scapulothoracic joint to overall shoulder function, it is important to shoulder function, it is important to examine the scapulothoracic joint examine the scapulothoracic joint arthrokinematics, and muscle powerarthrokinematics, and muscle power

ExaminationExamination

Strength testingStrength testing– Localized, individual isometric muscle Localized, individual isometric muscle

tests around the shoulder girdle can tests around the shoulder girdle can give the clinician information about give the clinician information about patterns of weakness other than from patterns of weakness other than from spinal nerve root or peripheral nerve spinal nerve root or peripheral nerve palsies e.g., instabilities, postural palsies e.g., instabilities, postural dysfunction, and also help to isolate dysfunction, and also help to isolate the pain generatorsthe pain generators

ExaminationExamination

Examination of Movement Examination of Movement PatternsPatterns– These tests are concerned with the These tests are concerned with the

coordination, timing, or sequence of coordination, timing, or sequence of activation of the muscles during activation of the muscles during movementmovement

ExaminationExamination

Functional TestingFunctional Testing– The assessment of shoulder function The assessment of shoulder function

is an integral part of the is an integral part of the examination of the shoulder examination of the shoulder complexcomplex

– The term The term shoulder functionshoulder function can can include tests for biomechanical include tests for biomechanical dysfunction and tests assessing the dysfunction and tests assessing the patient’s ability to perform the basic patient’s ability to perform the basic functions of activities of daily livingfunctions of activities of daily living

ExaminationExamination

Other test for the shoulder Other test for the shoulder complex include:complex include:– Muscle Length TestsMuscle Length Tests – Examination of the passive restraint Examination of the passive restraint

system and neighboring jointssystem and neighboring joints– Special TestsSpecial Tests– Diagnostic and imaging studies Diagnostic and imaging studies

InterventionIntervention

Acute phase goals:Acute phase goals:– Protection of the injury siteProtection of the injury site– Restoration of pain-free range of motion in the Restoration of pain-free range of motion in the

entire kinetic chainentire kinetic chain– Improve patient comfort by decreasing pain Improve patient comfort by decreasing pain

and inflammationand inflammation– Retard muscle atrophyRetard muscle atrophy– Minimize detrimental effects of immobilization Minimize detrimental effects of immobilization

and activity restrictionand activity restriction– Maintain general fitnessMaintain general fitness– Patient to be independent with home exercise Patient to be independent with home exercise

programprogram

InterventionIntervention

Functional phase goals:Functional phase goals:– Attain full range of pain free motiAttain full range of pain free motionon– Restore normal joint kinematicsRestore normal joint kinematics – Improve muscle strength to within Improve muscle strength to within

normal limitsnormal limits – Improve neuromuscular controlImprove neuromuscular control – Restore normal muscle force couplesRestore normal muscle force couples