Limbs : Upper Limb 



93 



The elbow-joint contains, enclosed in a common capsule and with a common 

 synovial cavity, the humero-ulnar, radio-ulnar, and humero-radial articulations. 

 There are indications in the joint that the radial articulations were at one time dis- 

 tinct from the humero-ulnar, but for practical purposes the three may be considered 

 as forming one compound joint, and the capsule is attached to the humerus above, 

 while it reaches the ulna below and is also attached to the orbiculai band round the 

 head of the radius, to which bone it is not fastened. 



The inner and outer parts of the capsule, consisting of radiating fibres from the 

 two condyles, are termed the^ateral ligaments : the inner passes to the inner margins 

 of the olecranon and coronoid pro- 

 cesses, and the outer goes mainly 

 to decussate and blend with the 

 orbicular fibres, and partly to the 

 ulna behind this (Fig. 72). Be- 

 tween the lateral ligaments are 

 the anterior and posterior capsu- 

 lar fibres : posterior part is thin, 

 consisting of a single and incom- 

 plete layer of vertical fibres, while 

 the anterior portion of the capsu- 

 lar contains three layers ; deepest, 

 thin and incomplete, transversely 

 disposed : intermediate thick, ver- 

 tical, and complete : superficia 1 , 

 one or two bands of oblique fibres 

 running downwards and outwards 

 to be lost on the front of the 

 orbicular ligament. 



We have already seen (p. 87) 

 how the front capsule is attached 

 above the fossae on the humerus, while the posterior fibres gain the floor of the ole- 

 cranon fossa : below, the anterior capsular fibres make a marking on the coronoid 

 process a little distance below its upper border (Fig. 75), and the posterior fibres join 

 the olecranon a little way from its articular margin. 



Evidently the anterior and posterior fibres of the capsule can have little to do 

 with maintaining the articulation of the bones of the forearm with the humerus, and 

 a cursory examination of the articular surfaces will suffice to show that the greater 

 sigmoid cavity, deep as it is, does not grasp the trochlea to a sufficient extent to hold 

 the bones together without external help, so we are compelled to seek for the provision 

 of such assistance in the lateral ligaments. 



Fig- 73 shows the internal lateral ligament as a coarsely fasciculated group of 

 fibres radiating from the internal condyle ; the front fibres pass to the prominent 

 tubercle on the inner side of the coronoid process and the neighbouring bone, while 

 the posterior fibres go to the side of the olecranon. The intermediate fibres are not 

 strong, and the notch between the coronoid and olecranon is bridged by transverse 

 fibres (oblique ligament of Cooper). The anterior band is very strong, and is attached 

 above to the lower and front part (Fig. 68) of the internal condyle as far as its tip 

 that is, practically in the axis of rotation of the ulna on the humerus ; therefore 

 this band is in a state of nearly constant tension in all positions of the humero-ulnar 

 joint. 



Extern)! littnl fiff 



fiitnt gang (t crlnrulirKg'- 



Supintttf tm'i 

 FIG. 72. Capsule of elbow-joint seen from the outer side. 





