288 THE ARTICULATIONS, OR JOINTS 



of the second and third pieces of the sternum. This articulation may be provided 

 with two synovial membranes. In the other joints intra-articular ligaments may 

 exist, but they rarely completely divide the joint into two cavities. 



The anterior chondroxiphoid ligament (ligamentum costoxiphoidea) (Fig. 237) 

 is a band of ligamentous fibres which connects the anterior surface of the seventh 

 costal cartilage, and occasionally also that of the sixth, to the anterior surface of 

 the ensiform cartilage. It varies in length and breadth in different subjects. A 

 similar band of fibres on the internal or posterior surface, though less thick and 

 distinct, may be demonstrated. It is spoken of as the posterior chondroxiphoid 

 ligament. 



Synovial Membranes (Fig. 237). There is no synovial membrane between the first costal 

 cartilage and the sternum, as this cartilage is directly continuous with the sternum. There are 

 two synovial membranes, both in the articulation of the second and third costal cartilages to the 

 sternum. There is generally one synovial membrane in each of the joints between the fourth, 

 fifth, sixth, and seventh costal cartilages to the sternum; but it is sometimes absent in the sixth 

 and seventh chondrosternal joints. Thus, there are usually eight synovial cavities on each side 

 in the articulations between the costal cartilages of the true ribs and the sternum. After middle 

 life the articular surfaces lose their polish, become roughened, and the synovial membranes 

 appear to be wanting. In old age the articulations do not exist, the cartilages of most of the 

 ribs becoming continuous with the sternum. 



Movements. The movements which are permitted in the chondrosternal articulations are 

 limited to elevation and depression, and these only to a slight extent. 



Articulations of the Cartilages of the Ribs with Each Other (articulationes 

 interchondmles) (Fig. 237). The contiguous borders of the sixth, seventh, and 

 eighth, and sometimes the ninth and tenth, costal cartilages articulate with each 

 other by small, smooth, oblong-shaped facets. Each articulation is enclosed in 

 a thin capsular ligament lined by synovial membrane, and strengthened externally 

 and internally by ligamentous fibres, external and internal interchondral ligaments 

 (ligamenta intercostalia externa et interna), which pass from one cartilage to the 

 other. Sometimes the fifth costal cartilage, more rarely that of the ninth, articu- 

 lates, by its lower border, with the adjoining cartilage by a small oval facet; 

 more frequently they are connected together by a few ligamentous fibres. 

 Occasionally the articular surfaces above mentioned are wanting. 



Articulations of the Ribs with their Cartilages (Fig. 237). The outer 

 extremity of each costal cartilage is received into a depression in the sternal 

 ends of the ribs, and the two are held together by the periosteum. There is no 

 real joint. Occasionally a synovial membrane exists between the first rib and 

 the corresponding cartilage. 



VIII. Articulations of the Sternum (Fig. 237) 



The first piece of the sternum is united to the second either by an amphi- 

 arthrodial joint a single piece of true fibrocartilage uniting the segments or by 

 a diarthrodial joint, in which each bone is clothed with a distinct lamina of hyaline 

 cartilage, adherent on one side, free and lined with synovial membrane on the 

 other. In the latter case the cartilage covering the gladiolus is continued without 

 interruption on to the cartilages of the second ribs. 1 The two segments are 

 further connected by an 



Anterior Intersternal Ligament. Posterior Intersternal Ligament. 



1 Mr. Rivington has found the diarthrodial form of joint in about one-third of the specimens examined by 

 him; Mr. Maisonneuve more frequently. It appears to be rare in childhood, and is formed, in Mr. Rivington's 

 opinion, from the amphiarthrodial form by absorption. The diarthrodial joint seems to have no tendency to 

 ossify at any age, while the amphiarthrodial is more liable to do so, and has been found ossified as early as 

 thirty-four years of age. Professor Cunningham says: "It is not usual to find the manubrigladiolar joint 

 obliterated by the ossification of the two bony segments. Even in advanced life it remains open, and the joint 

 partakes of the nature of an amphiarthrosis, although a joint cavity is not found under any circumstances in the 

 plate of fibrocartilage .which intervenes between the manubrium and the gladiolus." 



