In addition well-defined anatomical spaces are also considered to be functional joints without which a normal movement in the shoulder girdle would not be possible.
Scapulocostal (Scapulothoracal Articulation) Joint
An articular surface is made by thoracal paries and interior fascies of a shoulder blade between which there is a muscular layer m. serratus anterior and m. subscapularis.
Tendon of the Long Head of the Biceps
A tendon of a long head of the biceps slides in sulcus bicipitalis humeri during all movements of the shoulder girdle. Only a free movement of this tendon makes possible the movement of the glenohumeral articulation without any restrictions.
A tendon of a long head of the humerus
Suprahumeral Articulation (Subacromial Articulation)
It is formed by space between the head of the humerus and the ligament connecting an acromion with processus coracoideus1. In this space the head of the humerus moves during all movements. Except muscular substance of a rotator cuff, there is also a subacromial bursa which under normal conditions makes possible a smooth movement of the head of the humerus. If this space is too narrow, it can lead to an incarceration of the rotator cuff by the acromion2.
1 ligamentum coracoacromiale
2 so-called impigement syndrome