498 APPLIED ANATOMY. 



shortening, while the former shows the apparent shortening. To identify the tip of 

 the internal malleolus is usually easy enough, but the anterior superior spine is not 

 so evident. The anterior portion of the crest of the ilium should be followed forward 

 until its anterior superior spine can be distinctly felt. In applying the tape it is 

 better not to rest it on the superficial surface of the spine nearest the skin but rather 

 on its inferior surface nearest the feet. It should be placed below the spine and then 

 pushed firmly upward and backward against its lower surface. The superficial sur- 

 face of the anterior superior spine is often so rounded or flat as to make it an uncer- 

 tain point to measure from. To put the parts in their normal position it is necessary 

 to see that a line joining the two anterior superior spines is at a right angle with the 

 long axis of the body, otherwise the tilting of the pelvis will vitiate the results. 

 Fig. 498, A, front view, shows the normal relation; g is the umbilicus; g-h, the 

 median line; <z, left anterior spine; 6, right anterior spine; c, left trochanter; d, right 

 trochanter; e, left internal malleolus; /, right internal malleolus. The line a-b is to 

 be at right angles to g-h. Then a-e = b-f and g-e = g-f. 



Fig. 498, B shows the effect of tilting of the pelvis, the legs being of equal length. 

 a-b instead of being at right angles to g-h is inclined upward on the left side and 

 down on the right. Apparent shortening is seen by comparing g-f with g-e. 

 Actual measurement shows a-e to be a trifle longer than b-f. This is accounted for by 

 the tilting causing b-d to approach each other while a-c have separated. 



If one hip is ankylosed its femur should be moved laterally until the line joining 

 the two anterior superior spines is at right angles to the median line of the body; 

 the opposite limb is then to be abducted to a similar degree and the measurements 

 of the two limbs can then be compared. 



When the legs are unequal and the pelvis is in a correct position, the apparent 

 and actual measurements agree (Fig. 498, C). 



When the legs are unequal the pelvis is tilted down on the side of the short leg 

 (Fig. 498, D}. Apparent length taken from the umbilicus shows the legs equal, but 

 the distance b-f will be found to be longer than a-e. This will not give accurately 

 the actual amount of shortening because of the tilting of the pelvis. It can only 

 be determined by levelling the pelvis so as to make the distances a-c and b-d equal. 



The length of the extremity below the neck of the femur can be determined by 

 feeling for the tip of the greater trochanter on its upper posterior border and measur- 

 ing to the external malleolus and comparing with the opposite side. 



WALKING. 



As locomotion is one of the main functions of the lower extremity, derange- 

 ments of this function are to be explained by a knowledge of the normal action of 

 its mechanism. The means by which support is accomplished have already been 

 explained in the maintenance of equilibrium. Locomotion embraces walking, run- 

 ning, jumping, etc. Of these walking is the fundamental movement, and the others 

 are only amplifications and modifications of it. In slow normal walking on a level 

 surface the thigh moves on the pelvis, the leg on the thigh, the foot on the leg, and 

 the toes on the rest of the foot. These movements are almost solely in an antero- 

 posterior direction, there being almost no lateral or rotary movements ; these begin 

 only when the actions become violent and irregular, such as are necessary in running, 

 overcoming obstacles, etc. It is for this reason that a person may have no limp when 

 walking slowly, but a very perceptible one when walking rapidly. There is always 

 a small amount of lateral motion present which varies with the individual and the sex. 



As slow walking necessitates mainly anteroposterior motion, it can be explained 

 by viewing the body laterally. 



In ordinary walking the body inclines forward 5 degrees, in fast walking 10 

 degrees, and in running about 22 degrees (Weber). In walking (Fig. 499, A) the 

 body is inclined forward and at the same time one leg begins to advance (the right). 

 This causes flexion of the left ankle and flexion of the right hip (Fig. 499, B and C). 

 As the right foot touches the ground it extends and the right knee flexes to avoid 

 the shock of impact (Fig. 499, Z>), the left knee begins to flex and flexes more than 

 the right in order for the left foot to swing clear of the ground while being advanced ; 



