Shoulder anatomy

The shoulder is one the most complicated and sophisticated joints of the body, while it is also the most mobile and the most unstable joint of the human body. It has the greatest range of motion with complete global movement allowing precise guidance of the gestures of the arm and the hand.

The shoulder is an articular complex composed of 4 joints :

  • The Glenohumeral joint connects the bone of the arm (the humerus) to the glenoid of the scapula ; it has a major role in the function of the arm.
  • The Acromioclavicular joint connects the acromion to the lateral end of the clavicle.
  • The Sternoclavicular joint connects the upper limb to the thorax.
  • The Scapulothoracic joint represents a sliding space between the scapula and the thorax.

Ligaments of the shoulder

The ligaments of the shoulder are numerous around the glenohumeral joint. Their weakness can cause shoulder instability.
Recurrent dislocations aggravate lesions of the lower glenohumeral ligament, which has a major role in shoulder stability.

Muscles and tendons

The great mobility of the shoulder is the result of the coordinated action of the five muscles of the rotator cuff : Supraspinatus, Infraspinatus, Teres minor, Subscapularis and the long head of biceps. Each of the muscles of the rotator cuff is attached to the joint by a tendon.

Below, an animation to better understand the anatomy of the shoulder (in French)