- 📖 Geeky Medics OSCE Book
- ⚡ Geeky Medics Bundles
- ✨ 700+ OSCE Stations
- ✅ OSCE Checklist PDF Booklet
- 🧠 Medical Finals Questions
- 💊 PSA Questions
- 💉 Clinical Skills App
- 🗂️ Flashcard Collections | OSCE, Medicine, Surgery, Anatomy
To be the first to know about our latest videos subscribe to our YouTube channel 🙌
Table of Contents
Introduction
The shoulder, or glenohumeral joint, connects the upper arm to the chest. It provides articulation between the glenoid fossa of the scapula and the head of the humerus. These articulating surfaces are separated by a narrow cavity filled with synovial fluid, making it a synovial joint.
The shoulder joint is an example of a ball and socket joint, which is highly mobile due to the minimal contact between its two articulation points, allowing for a wide range of movement. This extra mobility does, however, come at the expense of joint stability.
The shoulder joint is made up of several structures including:
- Bones: scapula, humerus and clavicle
- Muscles: rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis), deltoid, pectoralis major, teres major
- Ligaments: glenohumeral, coracohumeral, coracoacromial
Bony structure
The shoulder joint is comprised of three bones, the humerus, scapula, and clavicle.
Humerus
Proximal articulation: with the glenoid fossa of the scapula
Distal articulations:
- Laterally, the capitulum articulates with the head of the radius
- Medially, the trochlea articulates with the trochlear notch of the ulna
The humerus has both an anatomical neck and a surgical neck:
- The anatomical neck is the site of attachment of the joint capsule
- The surgical neck is found inferior to the head of the humerus
Scapula
The scapula acts as the point of attachment for the rotator cuff muscles.
Proximal articulation: the clavicle
Distal articulation: the head of the humerus
Clavicle
The clavicle is an S-shaped bone which is contoured by the many muscles which attach to it. It is also the most commonly fractured bone in the body.
Proximal articulation: the manubrium
Distal articulation: the acromion of the scapula
Clinical relevance: Shoulder dislocation
Dislocation, or subluxation, of the shoulder joint, is a relatively common injury. Anterior dislocation of the shoulder joint (95% of cases) is caused by excessive extension and lateral rotation of the humerus. It most commonly occurs in males aged 16-20 years old.
A serious complication of shoulder dislocation is axillary nerve injury. The axillary nerve runs along the surgical neck of the humerus. Injury to this nerve causes paralysis of the deltoid muscle and loss of sensation over the ‘regimental badge’ area.
Ligaments
The shoulder joint includes the following ligaments:
- Glenohumeral ligaments (x3)
- Coracohumeral ligament
- Coracoacromial ligament
Glenohumeral ligament
There are three glenohumeral ligaments that run between the glenoid fossa of the scapula and the head of the humerus – the superior, medial, and inferior ligaments. Their job is to stabilise the shoulder joint.
Medial glenohumeral ligament
Origin: the medial edge of the glenoid fossa
Insertion: the lesser tubercle of the humerus
Superior glenohumeral ligament
Origin: the apex of the glenoid fossa
Insertion: the lesser tubercle of the humerus
Inferior glenohumeral ligament
Origin: the lower edge of the glenoid fossa
Insertion: the anatomical neck of the humerus
Coracohumeral ligament
The coracohumeral ligament is divided into a superior and inferior band. Both of these bands function to strengthen the upper joint capsule.
Superior band
Origin: the coracoid process
Insertion: the superior band forms a common insertion with the tendon of supraspinatus on the greater tubercle
Inferior band
Origin: the coracoid process
Insertion: the lesser tubercle of the humerus
Coracoacromial ligament
The coracoacromial ligament is clinically important as it prevents superior dislocation of the humeral head of the shoulder joint.
Origin: the coracoid process of the scapula
Insertion: the acromion
Bursae
The shoulder joint contains a few fluid-filled sacs called synovial bursae. The function of these is to minimise friction between the articulating surfaces. The bursae located in the shoulder joint include:
- Subacromial-subdeltoid bursa: located between the joint capsule and the deltoid muscle
- Subacromial bursa: located between the joint capsule and the acromion
- Subcoracoid burse: located between the joint capsule and the coracoid process
Clinical relevance: Subacromial bursitis
The subacromial bursa lies between the joint capsule and the acromion of the scapula. It functions to reduce friction between these two structures.
Subacromial bursitis refers to inflammation of this bursa, often developing as a result of repetitive overhead abduction of the shoulder. It commonly presents as a form of impingement syndrome, with associated pain, weakness and stiffness of the shoulder joint. See the Geeky Medics shoulder examination guide for more details.
Rotator cuff muscles
There are several muscles that act to move the shoulder joint. The most notable and clinically important are the rotator cuff muscles. Their main function is to stabilise the shoulder joint and allow its excessive range of motion.
Supraspinatus
Origin: the supraspinous fossa
Insertion: the superior facet of the greater tubercle of the humerus
Function: abduction of the humerus
Innervation: suprascapular nerve (C5)
Vascular supply: suprascapular artery
Infraspinatus
Origin: the infraspinous fossa
Insertion: the middle facet of the greater tubercle of the humerus
Function: external rotation of the humerus
Innervation: suprascapular nerve (C5)
Vascular supply: suprascapular artery, circumflex scapular artery
Subscapularis
Origin: the subscapular fossa
Insertion: the lesser tubercle of the humerus
Function: internal rotation of the humerus
Innervation: upper and lower subscapular nerve (C5/6)
Vascular supply: subscapular artery
Teres minor
Origin: the lateral border of the scapula
Insertion: the inferior facet of the greater tubercle of the humerus
Function: external rotation of the humerus
Innervation: axillary nerve (C5)
Vascular supply: posterior circumflex humeral artery, circumflex scapular artery
Clinical relevance: Impingement syndrome
Impingement syndrome is caused by rotator cuff tendonitis as the tendons pass beneath the acromion. The supraspinatus muscle’s tendon is most commonly affected.
Impingement syndrome typically presents with pain, weakness and restricted shoulder movement. Patients with impingement syndrome often complain of pain when their arms are raised (this is particularly common in mechanics and manual labourers who work with their arms overhead). When the arm is raised, the subacromial space narrows, which can result in impingement of the supraspinatus muscle tendon leading to an inflammatory response.
Clinical examination
Typical findings on clinical examination in supraspinatus impingement syndrome include:
- Pain experienced between 60-120° of shoulder abduction (known as a ‘painful arc’).
- Weakness and pain experienced when the supraspinatus muscle is isolated using the ‘Empty can/Jobe’s test
For more information, see the Geeky Medics shoulder examination guide.
Other muscles of the shoulder
Deltoid
The deltoid is a large and triangular-shaped muscle. The deltoid muscle plays a significant role in both the range of shoulder joint movement and in preventing joint dislocation when carrying heavy objects.
Origin: the anterior border of the clavicle, acromion and spine of the scapula
Insertion: the deltoid tuberosity of the humerus
Function: abduction, flexion and extension of the shoulder
Innervation: axillary nerve
Vascular supply: posterior circumflex humeral artery
Teres major
Origin: the posterior aspect of the inferior angle of the scapula
Insertion: the intertubercular sulcus of the humerus
Function: internal rotation and adduction of the shoulder
Innervation: lower subscapular nerve
Vascular supply: subscapular and circumflex scapular artery
Pectoralis major
Pectoralis major is a large muscle located on the anterior chest wall that has several shoulder joint related functions. This muscle works in combination with pectoralis minor which lies underneath it.
Origin: the clavicular head
Insertion: the bicipital groove of the humerus
Function: flexion, adduction and internal rotation of the humerus
Innervation: lateral and medial pectoral nerve
Vascular supply: pectoral branch of the thoracoacromial trunk
Latissimus dorsi
Origin: lower thoracic vertebrae (T8-12), lumbar vertebrae, ribs 9-12, iliac crest
Insertion: the intertubercular sulcus of humerus
Function: extension, adduction and internal rotation of the humerus
Innervation: thoracodorsal nerve
Vascular supply: thoracodorsal branch of the subscapular artery
Table 1. Table showing muscles of the shoulder joint and the movements that they produce.
Movements of the shoulder
Below is a brief overview of which muscles are involved in specific shoulder movements.
| Movement | Muscles involved |
| Abduction |
Supraspinatus Deltoid |
| Adduction |
Pectoralis major Teres major Latissimus dorsi Subscapularis |
| Internal rotation |
Subscapularis Teres major Deltoid Pectoralis major Latissimus dorsi |
| External rotation |
Deltoid Infraspinatus Teres minor |
| Flexion |
Pectoralis major Deltoid |
| Extension |
Deltoid Latissimus dorsi |
Reviewer
Ishani Sinha
Junior Doctor
Editor
Arunachalam Soma
References
- Richard Drake, A. Wayne Vogl, Adam Mitchell. Gray’s Anatomy for Students (4th Edition). Published in 2019. Available from: [LINK]
- Athwal, G. OrthoInfo. Rotator Cuff Tears. Published in 2017. Available from: [LINK]
- Bogart, Bruce. Elselvier’s Integrated Anatomy and Embryology. Published in 2007. Available from: [LINK]
- Mayo Clinic. Dislocated Shoulder. Published in 2018. Available from: [LINK]
- Openstax. Anatomy and Physiology. Published in 2013. Available from: [LINK]
- Bduttabaruah, Wikipedia. Anterior View of the Left Humerus. Licence: [CC BY-SA]. Available from: [LINK]
- OpenStax Anatomy and Physiology. The Scapula. License: [CC BY-SA]. Available from: [LINK]
- Hellerhoff. Anterior Dislocation of the Shoulder. License: [CC BY-SA]. Available from: [LINK]
- OpenStax Anatomy and Physiology. Coronal view of the Shoulder Joint. License: [CC BY-SA]. Available from: [LINK]
- OpenStax Anatomy and Physiology. Muscles of the Pectoral Girdle. License: CC BY-SA. Available from: [LINK]
- Mikael Häggström, used with permission. Available from: [LINK].
- Anatomography. Subscapularis and teres minor muscles. License [CC BY-SA 2.1 JP]. Available from [LINK].
- OpenStax College. Deltoid muscle. Licence: [CC BY]. Available from: [LINK].
