266 THE ARTICULATIONS OR JOINTS. 
consists of similarly-disposed, but not so strong, oblique fibres situated on the 
posterior aspect of the articulation. 
A fibro-cartilaginous meniscus (discus articularis, Fig. 207) divides the joint 
cavity into two compartments. It is nearly circular in shape, and adapts itself to 
the articular surfaces between which it les. It is thickest at the circumference and 
thinnest at the centre, where it occasionally presents a perforation, thereby 
permitting the two synovial cavities to intercommunicate. By its circumference it 
is in contact with, and adherent to, the surrounding capsule, but its upper margin is 
attached to the apex of the articular surface of the clavicle, while by its lower 
margin it is fixed to the sternal end of the first costal cartilage. 
Two accessory ligaments are associated with this joint, viz. the interclavicular 
and the rhomboid. 
The interclavicular ligament (Fig. 207) is a structure of considerable strength, 
forming a broad band of fibrous tissue which is attached to the superior rounded angle 
or apex of the sternal end of the clavicle as well as to the adjacent margins of the 
articular surface. Its fibres pass across the interclavicular notch to become attached 
to corresponding parts of the opposite clavicle, but in their course they dip down into 
the supra-sternal notch, in which many of them are fixed to the sternum. In this 
way their presence neither bridges nor obliterates the notch between the two 
clavicles, and the ligament really becomes a superior sterno-clavicular ligament for 
each joint. 
The rhomboid ligament (lig. costo-claviculare, Fig. 207) consists of short, strong 
fibres which are attached inferiorly to the upper surface of the first costal cartilage. 
They pass obliquely upwards and outwards to a rough impression situated on the 
lower aspect of the sternal end of the clavicle, and are distinct from the capsular 
ligament. Occasionally a bursa is found in the interior of this hgament. 
As arule, there are two synovial membranes lining the two joint cavities (Fig. 
207), separated from each other by the interarticular meniscus. Sometimes, however, 
the two membranes establish continuity through a perforation in the meniscus. 
THE ACROMIO-CLAVICULAR OR SCAPULO-CLAVICULAR JOINT. 
The acromio-clavicular joint (articulatio acromio -clavicularis) is another 
instance of an arthrodial diarthrosis. It is situated between the acromial end of 
the clavicle and the inner aspect of the acromion process of the scapula. Hach 
articular surface is an oval, flattened facet, covered by fibro-cartilage. 
The ligaments which surround this small joint form a complete capsule 
(capsula articularis), of which the upper and lower parts are specially strong, and 
are therefore named the superior and inferior acromio-clavicular ligaments (Fig. 209). 
These consist of short fibres passing between the adjacent rough margins of the 
two bones in the positions indicated by their names. 
A meniscus (discus articularis), which is nearly always incomplete, and may 
occasionally be wanting, is usually found within the joint cavity, where it lies 
obliquely, with its upper margin farther from the mesial plane than its lower 
margin, and having its borders ‘attached to the surrounding capsule. Frequently 
the meniscus is wedge- shaped, with its base directed upwards and its apex free. 
A synovial membrane is found for ming either a single or a double sac, according to 
the condition of the meniscus. Complete division of the joint cavity, however, is rare, 
Ligamentum Coraco-claviculare.—Accessory to this articulation there is the 
strong coraco-clavicular ligament which binds the acromial end of the clavicle to 
the coracoid process of the scapula. It is readily divisible into two parts, viz. the 
conoid and trapezoid ligaments. 
The conoid ligament (Fig. 209) is situated internal to and slightly behind the 
trapezoid. It is narrow and pointed at its inferior end, by which it is attached 
to the upper aspect of the coracoid process, in close proximity to the supra-scapular 
notch. Its upper end widens out in the manner expressed by its name, and is 
attached to the conoid tubercle of the clavicle. 
The trapezoid ligament (Fig. 209) is attached inferiorly to the upper surface of the 
posterior half of the coracoid process, external and anterior to the attachment of 
