Shoulder Region

Musculoskeletal overview

Authors
Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Thorax and Shoulder girdle (posterior view)
Reading list
  • General
    • Ch16 Shoulder
    • Sport therapy for the shoulder: evaluation, rehabilitation, and return to sport
  • Examination
    • Ch19 Screening the Shoulder and Upper Extremity
  • Manual Tx
    • Ch22 Orthopaedic Manual Physical Therapy of the Shoulder Joint Complex
  • Surgery
    • Synopsis of Shoulder.

There are 3 major axes of the shoulder:

  1. Transverse Axis: Allows movements of flexion and extension in the sagittal plane
  2. Antero-posterior axis: Allows movements in the frontal plane
  3. Vertical axis: runs through the intersection of the sagittal and frontal planes and controls the movements of flexion and extension.

Bones

The Shoulder complex is made up of 3 bones:

  1. Humerus
  2. Clavicle
  3. Scapula

Humerus

Read more about the humerus here

Clavicle

Figure 2: Left Clavicle (superior view)
Figure 3: Left clavicle (inferior view)

Read more about the clavicle here

Scapula

Figure 4: Left Scapula (Anterior view)
Figure 5: Left scapula (Posterior view)
Figure 6: Left Scapula (Lateral view)

Read more about the scapula here

Joints

The Shoulder complex is made up of 3 joints and 1 pseudo joint:

  1. SCJ provides gross movement of the clavicle.
  2. The ACJ provides fine motor control of the clavicle.
  3. The glenohumeral joint
  4. The scapulothoracic (pseudo) joint
Figure 7: Left Acromioclavicular and Glenohumeral joints (anterior view)
Figure 8: Right Glenohumeral joint capsule (Anterior view)

Sternoclavicular Joint

Read more about the Sternoclavicular (SCJ) here

Acromioclavicular joint

The acromioclavicular joint (ACJ) is an articulation

The ACJ has poor stability since the joint surfaces do not interlock making it prone to dislocations.

The acromion aspect of the joint is slightly convex and faces supero-antero-medially. The clavicular aspect is flat or slightly convex and faces infero-postero-laterally

Since these two facets can be flat or even both convex, they have poor joint congruity and in 30% of cases, an intra-articular fibrocartilage meniscus is present to improve congruency.

This joint’s stability is augmented by 2 extra-articular ligaments for stability: trapezoid lig. and conoid lig..

Read more about the Acromioclavicular joint (ACJ) here

Glenohumeral joint

Read more about Glenohumeral Joint (GHJ)

Scapulothoraic Joint

The Scapulothoracic Joint is considered a “pseudo joint”

Read more about the Scapulothoracic joint (STJ) here

Physiologic Area

  • Suprahumeral/Subacromial space

Ligaments

“(GH Ligs) Together with the coracohumeral ligament, these ligaments form a Z-pattern on the anterior aspect of the shoulder (Fig. 16-6).3 In the midrange of rotation, the G-H ligaments are relatively lax”

Flexion & Extension

Flexion and extension are movements of the shoulder that occur in the sagittal plane about a transverse axis.

Normal ROM for shoulder flexion and extension
Movement GHJ Scapulohumeral Total
Extension 45-50°
Flexion 120° 60° 180°

Abduction & Adduction

Abduction and adduction of the shoulder refers to frontal/coronal plane movement occurring about an antero-posterior axis.

Normal abduction is 180°.

During abduction, the should complex made up of the GHJ, ACJ and STJ work together in 3 distinct phases to complete the whole range of motion.

  1. 0-60° abduction takes place only at the glenohumeral joint.
  2. 60-180° is a combination of glenohumeral joint and the scapulothoracic joint.

Abduction

There are 4 abductor muscles that form a force coupling of shoulder abduction.

  • Glenohumeral
    • deltoid
    • Supraspinatus
  • Scapulothoracic joint (upward rotation)
    • Serratus anterior
    • Upper trapezius

During abduction, the subscapularis, infraspinatus, and teres minor draw the humeral the infero-medially during abduction.

Note

The biceps brachii long head is also involved in abduction and a rupture will result in ~20% decrease in abduction strength.

Pure abduction

Pure abduction occurs in the frontal plane.

  • Component III of lateral deltoid recruits first
  • IV and V of posterior deltoid recruit immediately after.
  • Component II (anterior delt) recruits after the first 20-30°.

Scapular plane abduction

Scapular plane exists between the sagittal and frontal planes. 30° from the frontal plane.

  1. II (anterior deltoid) and III (lateral deltoid) are recruited first.
  2. IV and V (posterior deltoid) and I (Anterior deltoid) are recruited progressively later.

External rotation into abduction

  1. II (anterior deltoid) contracts at the start
Note

IV and V (Posterior deltoid) do not contract at all during this movement.

IR to abduction

“recruitment order reverses”.

Axial Rotation

The “neutral” position in axial rotation is where the elbow is flexed to 90° and the forearm is in the sagittal plane.

Note

Another “neutral” position is at 30° of internal rotation where the rotator muscles are at equilibrium.

External rotation

Horizontal abduction & adduction

Stabilization

Passive

The shoulder maintains its passive stability by using multiple structures arranged reciprocally so when one structure is lax, the other is tightened. This allows the shoulder to have large degrees of freedom and ROM while limiting translation and rotation of the GHJ surfaces.

  • GH ligaments
  • Capsule
    • Posterior capsule
  • Glenoid labrum

Active

  • GHJ
    • RTC
  • Shoulder elevation
    • Rhomboids
    • SA

Bursae

According to Dutton, the synovium of the GH Joint Capsule forms multiple bursae in shoulder complex.

  • Subacromial bursae (Subdeltoid Bursae)
    • Lies on the superior aspect of the joint
    • Largest bursae of the shoulder complex

“It also forms variously sized bursae, the largest of which, the subacromial or subdeltoid bursa, lies on the superior aspect of the joint (see later).”

Muscles

Transverse muscles ( )press the humeral head against the glenoid cavity.

The longitudinal muscles () support the upper limb and prevent inferior disarticulation when carrying heavy objects. These muscles act to maintain or return the humeral head to the glenoid.

Table 2: Longitudinal Shoulder muscles
Muscle Origin Insertion Innervation Action
Anterior deltoid Lateral third of clavicle Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Flexion, IR, Adduction
Biceps brachii Long head Supraglenoid tubercle of scapula
Adjacent rim of Glenoid Labrum		 Radial tuberosity
Bicipital aponeurosis		 Musculocutaneous n.
C5 - C6		 Elbow: Flexion, Supination
GHJ: Flexion, Stabilization of humeral head during deltoid contraction, Abduction, IR
Biceps brachii Short head Coracoid process Radial tuberosity
Bicipital aponeurosis		 Musculocutaneous n.
C5 - C6		 Elbow: Flexion, Supination
GHJ: Flexion, Stabilization of humeral head during deltoid contraction, Abduction, IR
Lateral deltoid Acromion Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Abduction
Pectoralis major Clavicle (medial half)
Sternum
Costal cartilages 1-6
Rectus sheath (anterior layer)		 Humerus (crest of greater tubercle) Lateral pectoral n.
Medial pectoral n.
C5 - T1		 Entire muscle: Adduction, IR
Clavicular & Sternocostal parts: Flexion, Aids in respiration when shoulder is fixed
Posterior deltoid Scapular spine Deltoid tuberosity of humerus Axillary n.
C5 - C6		 GHJ: Extension, ER, Abduction
Triceps brachii lateral head Posterior humerus just *proximal* to radial groove
Lateral intermuscular septum		 Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension
Triceps brachii Long head Infraglenoid tubercle of Scapula Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension
GHJ: Extension, Adduction
Triceps brachii medial head Posterior humerus just distal to radial groove
Medial intermuscular septum		 Olecranon of Ulna Radial n.
C6 - C8		 Elbow: Extension

Stabilization

  • Anterior shoulder
    • Coracobrachialis

Pain

  • Clinical Considerations of Upper Back Shoulder and Arm Pain

MMT

Reading list
  • Flexion MMT
  • ext MMT
  • Abduction MMT
  • Adduction MMT
  • Horizontal abd MMT
  • Hor adduction MMT

Biomechanics

Arm Elevation

  • SCAP UR: end range: post tilt and ER
    • End position: inf angle at midaxillary line
  • GHJ: humeral elevation and lateral rotation, inf glide of humerus
  • SCJ: elevation and post rotation and retraction

Evaluation Inventory

Prone

Supine

Treatment

Prone

Supine

Special tests

Important

Special tests are useful when attempting to diagnose the integrity of a certain structure, but should not distract you from taking an inventory of all of the surrounding structures.

  • RTC
    • Subscap: Bear hug, Liftoff test
    • Champagne test
    • Hornblower’s test
  • Labral tear
    • Clunk test
  • SLAP Tear
    • Speed’s test (and bicipital tendinitis)
    • O’brien’s test
  • Anterior impingement
    • Hawkins-Kennedy test
  • Posterior impingement
    • Posterior internal impingement test
  • Posterior instability
    • Jerk test
  • Inferior instability
    • Sulcus sign
  • Anterior dislocation
    • Apprehension Test (Crank test)
    • Fulcrum test
  • Posterior dislocation

Diagnosis

Considerations before using special tests:

Special tests for the shoulder have multiple issues.

Poor Gold Standards

  • Poor convergent validity: Special tests for the shoulder are based on MRI and ultrasounds, which are poor gold standards.

Poor Tissue Isolation (Specificity)

  • In empty can for “ supra” 9 shoulder mm active,
  • During full can test 8 other mm were active

Pain is unreliable

  • Hyperalgesia: Areas with increased inflammatory markers can cause unrelated areas to be sensitive to certain positions. For example the subacromial bursa has high concentrations of substance P and pro-inflammatory cytokines and is often aggravated by the Empty can test.
  • Allodynia: Pain is not directly related to tissue damage.

ROM interventions

Exercise Movement Scapula
T 30° above the transverse plane
scapular plane flexion		 retraction
Y Scapular flexion Retraction + upward rotation + posterior tilt
I Pure Flexion Retraction + upward rotation + posterior tilt
  • Shoulder Ws
  • Shoulder WERs

References

1.
Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/
2.
Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.
3.
Ellenbecker TS, Wilk KE. Sport Therapy for the Shoulder: Evaluation, Rehabilitation, and Return to Sport. Human Kinetics; 2017.
4.
Heick J, Lazaro RT. Goodman and Snyder’s Differential Diagnosis for Physical Therapists: Screening for Referral. 7th edition. Elsevier; 2023.
5.
Wise CH, ed. Orthopaedic Manual Physical Therapy: From Art to Evidence. F.A. Davis Company; 2015.
6.
Srikumaran U. Synopsis of Shoulder Surgery. Thieme; 2021.
7.
Jones B. B Project Foundations. b Project; 2025.
8.
Neumann DA, Kelly ER, Kiefer CL, Martens K, Grosz CM. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017.
9.
Donnelly JM, Simons DG, eds. Travell, Simons & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Third edition. Wolters Kluwer Health; 2019.
10.
Weinstock D. NeuroKinetic Therapy: An Innovative Approach to Manual Muscle Testing. North Atlantic Books; 2010.

Citation

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