THE ELBOW-JOINT. 2771 
Since these axes all pass through the shoulder-joint, and since each may present varying 
. - . 5 . ) . . . ~ —) 
degrees of obliquity, it follows that very elaborate combinations are possible until the movement 
oi pe 
of circumduction is evolved. In this movement the head of the humerus acts as the apex of a 
cone of movement with the distal end of the humerus, describing the base of the cone. 
The range of the shoulder-joint movements is still, further increased from the mobility of 
the scapula as a whole, and from its association with the movements of the clavicle already 
described. 
THE ELBOW-JOINT. 
This articulation (articulatio cubiti) provides an instance of a diarthrosis capable 
of performing the movements of flexion and extension about a single axis placed 
transversely, 7.e. a typical ginglymus diarthrosis or hinge-joint. 
The bones which enter into its formation are the humerus, ulna, and radius. 
The trochlea of the humerus articulates with the greater sigmoid cavity of the 
ulna (articulatio humero-ulnaris); the capitellum of the humerus articulates with 
the shallow depression or cup on the superior aspect of the head of the radius (articu- 
latio humero-radialis). The articular cartilage clothing the trochlea of the humerus 
terminates in a sinuous or concave margin both anteriorly and posteriorly, so that 
it does not line either the 
coronoid or the olecranon 
fossa. Internally, it merely 
rounds off the inner margin 
of the trochlea, but exter- 
nally it is continuous with 
the encrusting cartilage 
covering the capitellum, to 
the margin of which the 
cartilage extends in all 
directions, and thus it pre- 
sents a convex edge in Anterior 
° : igament 
relation to the supra-capi- ~ 
 tellar or radial fossa. The 
cartilage which lines the 
greater sigmoid cavity of 
the ulna presents a trans- External 
verse interruption, consider- jige vane 
ably wider on its inner as 
compared with its outer 
aspect. Thereby the coro- Guia 
noid and olecranon seg- ligament 
ments of the fossa are 
separated from each other. 
‘The cartilage which clothes 
the coronoid segment is 
continuous with that which Hediug 
clothes the lesser sigmoid 
cavity. The shallow cup- 
shaped depression on the : 
_ head of the radius is covered ql 
by cartilage which rounds ge 
off the margin, and is pro- Fic. 211.—ANTERIOR VIEW OF ELBOW-JOINT. 
longed without interruption 
upon the vertical aspect of the head, descending to its lowest level on that part 
opposed to the lesser sigmoid cavity. 
_ Ligaments.—Taken as a whole, the ligaments form a complete capsule (capsula 
articularis), which is not defective at any point, although it is not of equal thick- 
“ness throughout, and certain bands of fibres stand out distinctly because of their 
greater strength. 
The anterior ligament (Fig. 211) consists of a layer whose fibres run in several 
Humerus 
Internal lateral 
ligament 
Tendon of insertion ot 
biceps muscle 
Oblique (ulno-radial) 
ligament 
eae ee Se 
Une 
