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CHAPTER VIII. 
Plate XI.— the hip, knee and ankle joints. 
Fig. 1. The capsular ligament is here opened in order to show 
the ligament of the hip, named the round ligament. It allows con¬ 
siderable latitude of motion, at the same time that it is the great 
safeguard against dislocation. 
Fig. 2 and 4. The crucial or internal ligaments of the knee-joint 
arise from each side of the depression between the condyles of the 
thigh-bone ; the anterior is fixed into the centre, the posterior into 
the back of the articulation of the tibia. This structure properly 
limits the motions of the joint, and gives the firmness requisite for 
violent exertions. Viewing the form of the bones, we should con¬ 
sider it one of the weakest and most superficial, but the strength of 
its ligaments and the tendons passing over it, render it the most 
secure, and the least liable to dislocation of any joint in the whole 
body. 
Fig. 3. One of the mterarlicidar cartilages of the knee, from their 
shape called semilunar ; it is also represented in situ, Fig. 2. The 
outer edge of each cartilage is thick, the inner concave edge thin; 
the sockets for the condyles of the thigh-bone are thus rendered 
deeper, and the cartilages are so fixed as to allow a little play on 
the tibia, by which the joint moves with great freedom. 
A moving cartilage is not common, but is peculiar to those joints 
whose motions are veiy frequent, or which move under a great 
weight. It is a contrivance found at the jaw-bone, the inner head 
of the collar-bone and the articulation of the wrist, as well as at the 
knee. The obvious use is to lessen friction and facilitate motion. 
Fig. 4. a, the fibida; b, the tibia, the lower extremities of which, 
c, d, form the outer and inner ankle, and receive, c, the great artic¬ 
ulating bone of the foot, called the astragalus between them. When 
the foot sustains the weight of the body the joint is firm, but when 
raised it easily rolls on the ends of these bones, so that the toe is 
directed to the place on which we intend to step. 
