Learning Objectives
By the end of this section, you should be able to:
- Describe the anatomical position and function of the scapula
- Identify the key bony landmarks on its costal, lateral, and posterior surfaces
- Explain the articulations of the scapula
- Recognise the clinical significance of scapular fractures
The scapula, commonly known as the shoulder blade, is a flat, triangular bone that forms a critical link between the upper limb and the trunk. It articulates with the humerus at the glenohumeral joint and with the clavicle at the acromioclavicular joint, allowing a wide range of shoulder movements.
The scapula provides attachment for 17 muscles, including those forming the rotator cuff, making it essential for both stability and mobility of the shoulder girdle.
Costal (Anterior) Surface
The costal surface of the scapula faces the rib cage.
Subscapular fossa
- A large, smooth, concave depression occupies most of the anterior surface. It serves as the origin of the subscapularis muscle, a key component of the rotator cuff.
Coracoid process
A hook-like projection arising from the superolateral aspect of the scapula and lying inferior to the clavicle.
It provides attachment for:
- Pectoralis minor
- Coracobrachialis
- Short head of biceps brachii
Lateral Surface
The lateral surface faces the humerus and contains the articular structures of the shoulder joint.
Key landmarks include:
Glenoid fossa
- A shallow, pear-shaped cavity on the lateral border of the scapula. It articulates with the head of the humerus to form the glenohumeral joint.
Supraglenoid tubercle
- A roughened area superior to the glenoid fossa. It serves as the attachment site for the long head of the biceps brachii.
Infraglenoid tubercle
- A roughened area inferior to the glenoid fossa. It provides attachment for the long head of the triceps brachii.
Posterior Surface
The posterior surface of the scapula faces posteriorly and provides attachment for several muscles, including two of the rotator cuff.
Its defining features include:
- Spine of the scapula
A prominent ridge running transversely across the posterior surface, dividing it into superior and inferior regions. - Acromion
A lateral extension of the scapular spine that arches over the glenohumeral joint.
It articulates with the clavicle at the acromioclavicular joint. - Supraspinous fossa
A small, shallow depression superior to the spine.
It gives origin to the supraspinatus muscle. - Infraspinous fossa
A larger, convex area inferior to the spine.
It is the origin of the infraspinatus muscle.
Articulations
The scapula participates in two primary joints:
- Glenohumeral joint
Between the glenoid fossa of the scapula and the head of the humerus - Acromioclavicular joint
Between the acromion of the scapula and the clavicle
Clinical Relevance
Fractures of the Scapula
Scapular fractures are uncommon due to the protection provided by surrounding muscles and the thoracic cage. When present, they usually indicate high-energy trauma, such as:
- High-speed road traffic collisions
- Crushing injuries
- Severe sports-related trauma
Most scapular fractures are managed conservatively, as the surrounding musculature provides sufficient stability to allow healing without surgical fixation.
