322 THE ARTICULATIONS, OR JOINTS 



Movements. The only movements permitted in the phalangeal joints are flexion and exten- 

 sion; these movements are more extensive between the first and second phalanges than between 

 the second and third. The movement of flexion is very considerable, but extension is limited 

 by the anterior and lateral ligaments. 



ARTICULATIONS OF THE LOWER EXTREMITY. 



The articulations of the lower extremity comprise the following groups: 



I. The Hip-joint. VI. The Tarsometatarsal Articulations. 



II. The Knee-joint. VII. Articulations of the Metatarsal 



III. The Articulations between the Bones with each other. 



Tibia and Fibula. VIII. The Metatarsophalangeal Articu- 



IV. The Ankle-joint. lations. 



V. The Articulations of the Tarsus.! IX. The Articulations of the Phalanges. 



I. The Hip-joint (Articulatio Coxae) (Figs. 259, 260). 



This articulation is an enarthrodial or ball-and-socket joint, formed by the 

 reception of the head of the femur into the cup-shaped cavity of the acetabulum. 

 The articulating surfaces are covered by hyaline cartilage, that on the head of 

 the femur being thicker at the centre than at the circumference, and covering 

 the entire surface with the exception of a depression just below its centre for the 

 attachment of the ligamentum teres; that covering the acetabulum is much thinner 

 at the centre than at the circumference. This cartilage forms an incomplete 

 ring of a horseshoe shape, being deficient below, where there is a circular depres- 

 sion, which in the recent state is occupied by a mass of fat covered by synovial 

 membrane. The ligaments of the joints are the 



Capsular. Teres. 



Iliofemoral. Cotyloid. 



Transverse. 



The capsular ligament (capsula articularis) (Figs. 259 and 260) is a strong, dense, 

 ligamentous capsule, embracing the margin of the acetabulum above and surround- 

 ing the neck of the femur below. Its upper circumference is attached to the acetab- 

 ulum a short distance above and behind the cotyloid ligament, but in front it is 

 attached to the outer margin of the ligament, and opposite to the notch, where 

 the margin of this cavity is deficient, it is connected to the transverse ligament, 

 and by a few fibres to the edge of the obturator foramen. Its lower circumference 

 surrounds the neck of the femur, being attached, in front, to the spiral or anterior 

 intertrochanteric line; above, to the base of the neck; behind, to the neck of the 

 bone, about half an inch above the posterior intertrochanteric line. From this 

 insertion the fibres are reflected upward over the neck of the femur, forming a 

 sort of tubular sheath, the cervical reflection, which blends with the periosteum 

 and can be traced as far as the cartilage which covers the head of the femur. 

 On the surface of the neck of the femur some of these reflected fibres are raised 

 into longitudinal folds, termed retinacula. It is much thicker at the upper and 

 fore part of the joint, where the greatest amount of resistance is required, than 

 below and internally, where it is thin, loose, and longer than in any other part. 

 It consists of two sets of fibres, circular and longitudinal. The circular fibres, 

 zona orbicularis (Fig. 262), are most abundant at the lower and back part of the 



