THE LOWER EXTREMITIES. 



193 



injured. In dislocation the head may be behind or in 

 front of the acetabulum. Impacted hip, where the neck 

 of the femur has, in a fall, been driven into the head, is 

 common in old people. Sometimes, especially in young 

 children, the bone is infected, osteomyelitis. Sarcoma 

 occurs. Most tubercular disease of the hip originates at 

 the upper extremity of the femur, tuberculosis generally 



FIG. 78. 



FIG. 79. 



Fro. 78. Right knee-joint, posterior view. (Leidy.) 



FIG. 79. Right knee-joint, showing internal ligaments: 2, anterior crucial 

 ligament; 3, posterior crucial ligament; 4, transverse ligament; 6, 7, semilunar 

 fibroeartilages. (Leidy.) 



starting in the head and then attacking trie capsule and 

 the soft parts of the joint. If neglected, shortening of 

 the leg may result, in which case the bone has to be 

 broken and set at an angle in order to enable the child to 

 walk. 



Occasionally a bit of cartilage gets broken off in the 

 knee-joint and wedged between the bones, so that the 

 joint cannot be straightened. This is dislocation of the 

 semilunar cartilage and necessitates an operation for 

 removal of the piece. The cartilage will eventually be 

 replaced by fibrous tissue and in a few months the leg 



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