SECTION II 



THE ARTICULATIONS 



Bv HENRY MORRIS, M.A., M.B., Lond.: F.R.C.S.Eng. 



SENIOR SrR(.KON TO AND I,ATE LECTURER ON SURGERY (FORMERLY LECTURER ON ANATOMY) AT THE MIDDLESEX 



hospital; MEMBER OP THE COUNCIL AND OF THE COURT OF EXAMINERS OF THE ROYAL COLLEGE OF 



SURGEONS, ENGLAND; EXAMINER IN SURGERY IN THE UNIVERSITY OF LONDON 



THE section devoted to the Articulations or Joints deals with the union of tlie 

 various and dissimilar parts of the human skeleton. The following struc- 

 tures enter into the formation of joints. 



Bones constitute the basis of most joints. The articular ends are expanded, 

 and are composed of cancellous tissue, surrounded by a dense and strong shell of 

 compact tissue. This shell has no Haversian canals (the vessels of the cancellous 

 tissue turn back and do not perforate it), or large lacunse, and no canaliculi, and 

 is thus well adapted to bear pressure. The long bones articulate by their ends, 

 the flat by their edges, and the short at various parts on their surfaces. 



Thi' Cartilage Avhich covers the articular ends of the bones is called articular, 

 and is of tin* hyaline variety. It is firndy implanted on the bone b}^ one surface, 

 while the otlier is smooth, polished, and free, thus reducing friction to a mini- 

 nuun, while its slight elasticity tends to break jars. It ends abruptly at the edge 

 of the articulation, and is thickest over the areas of greatest pressure. 



Another form of cartilage, the white fibrous, is also found in joints: — 



(i) As interarticular cartilage in diarthrodial joints — viz., the knee, temporo- 

 mandibular, sterno-clavicular, radio-carpal, and occasionally in the acromio- 

 clavicular. It is interposed between the ends of the bones. ]iartially or completely 

 dividing tlie synovial cavity into two. It serves to adjust dissimilar bony surfaces, 

 adding to the security of, while it increases the extent of motion at, the joint; it 

 also acts as a Iniffer to V)reak shocks. 



(ii) As circumferential or marginal fibro-cartilages, which serve to deepen the 

 sockets for the reception of the heads of bones — e.g. the glenoid and cotyloid 

 litraments of the shoulder and hip. Another form of marginal plate is seen in the 

 glenoid ligaments of the fingers and toes, Avliich deepen the articulations of the 

 phalanges and add to their security. 



(iii) As connecting fibro-cartilage. The more pliant and clastic is the more 

 cellular form, and is found in the intervertebral discs; while the less yielding and 

 more fibrous form is seen in the sacro-iliac and i)ubic articulaticms, where there is 

 little or no movement. 



The Ligaments which bind the .bones together are strong bands of white 

 fibrous tissue, t'oniiing a more or less perfect capsule, round the articulation. They 

 are ))liant but inextensile, varying in shape, strength, and thickness according to 

 the kind of articulation into which they enter. They are closely connected with 

 the periosteum of the bones they unite. In some cases — as the ligamenta subflava 

 which unite jiarts not in contact— they are formed of yellow elastic tissue. 



The synovial membrane lines the interior of the fibrous ligaments, thus ex- 



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