INJURIES TO JOINTS 



sist of fine fibres of tough, flexible and inelastic tissue, 

 which run from bone to bone across the joint. 1 



Kinds of movement. The various kinds of move- 

 ment which joints permit us to make with our limbs 

 are chiefly bending, or flexion; straightening, or ex- 

 tension; turning as on an axis, or rotation; moving away 

 from the middle of the body, or abduction; towards the 

 middle line, or adduction; and swinging in a circle, or 

 circumduction. 



Joint injuries. Joints are points of weakness in the 

 skeleton, as shown by the fact that injuries to them 

 are much more numerous than to bones. Their weak- 

 ness is due to the difficulty 

 of combining freedom of 

 movement with strength. 

 When a severe wrench is 

 given a joint from which 

 pain and swelling result, it 

 is said to be sprained. In 

 sprains, the fibres of the 

 ligaments are more or less 

 torn and their blood-ves- 

 sels are ruptured. If the 

 injury is severe, there is 

 swelling and subsequent 

 black and blue discolora- 

 tion, due to the blood 



which has escaped from the ruptured blood-vessels. 

 Sprains heal slowly and may require even more care- 

 ful and prolonged treatment than fractures, in order 

 to prevent permanent stiffness and weakness. 2 



1 Where the capsular ligaments are loose, as at the elbow, there 

 is great danger of their being pinched when the joint is flexed or 

 extended. To avoid this, muscle fibres are inserted to pull the 

 loose portion of the capsular ligament out of the joint. 



9 In sprains, the ends of the bones are sometimes fractured. If 



FIG. 30. Dislocation of elbow. 

 (Scudder and Cotton.) 



