The quadrangular space is an anatomical space is the posterior axilla region. It provides a conduit for structures to pass between the axilla and the posterior compartment of the arm. In this article, we shall look at the anatomy of the quadrangular space – its borders, contents and clinical relevance. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Borders The quadrangular space is rectangular-shaped with four boundaries: Superior – inferior margin of teres minor. Lateral – surgical neck of the humerus. Medial – long head of triceps brachii. Inferior – superior aspect of teres major. By TeachMeSeries Ltd (2025) Fig 1Posterior view of the shoulder region, showing the quadrangular space. The subscapularis muscle lies anteriorly, and so cannot be seen on this view. Pro Feature - Dissection Images Prosection of the muscles of the posterior shoulder and upper arm, demonstrating the quadrangular space. Prosection of the muscles of the posterior shoulder and upper arm, demonstrating the quadrangular space. You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More Contents The quadrangular space is a passageway that allows structures to travel between the axilla and posterior compartment of the upper arm. It contains the axillary nerve and posterior circumflex humeral artery (and accompanying vein) as they travel into the posterior upper arm. By TeachMeSeries Ltd (2025) Fig 2Contents of the quadrangular space; the axillary nerve and posterior circumflex humeral artery. Quadrangular Space Syndrome Quadrangular space syndrome refers to compression of the axillary nerve and posterior circumflex humeral artery as they pass through the quadrangular space. Compression is thought to occur secondary to hypertrophy of the muscular borders of the space, or by the formation of fibrotic bands between the muscles. Clinical features include pain and paraesthesia in the distribution of the axillary nerve, as well as pain upon shoulder abduction and external rotation. Do you think you’re ready? Take the quiz below Pro Feature - Quiz The Quadrangular Space Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 1800 More Questions Available Upgrade to TeachMeAnatomy Pro Challenge yourself with over 1800 multiple-choice questions to reinforce learning Learn More Print Article Rate This Article