158 HIP JOINT. 



The expansion of the extensor tendon over the back of the fingers takej 

 the place of a posterior ligament. 



Actions. This articulation admits of movement in four different direc- 

 tions, viz. of flexion, extension, adduction, and abduction, the two latter 

 being limited to a small extent. It is also capable of circumduction. 



11. Articulation of the Phalanges. These articulations are ginglymoid 

 joints . they are formed by three ligaments. 



Anterior, Two lateral. 



The anterior ligament is firm and fibre-cartilaginous, and forms part of 

 the articular surface for the head of the phalanges. Externally it is 

 grooved for the reception of the flexor tendons. 



The lateral ligaments are very strong ; they are the principal bond of 

 connexion between the bones. 



The extensor tendon takes the place and performs the office of a poste- 

 rior ligament. 



Actions. The movements of the phalangeal joints reflexion and exten- 

 sion, these movements being more extensive between the first and second 

 phalanges than between the second and third. 



In connexion with the phalanges, it may be proper to examine certain 

 fibrous bands termed thecce or vaginal ligaments, which serve to retain the 

 tendons of the flexor muscles in their position upon the flat surface of their 

 bones. These fibrous bands are attached at each side to the lateral mar- 

 gins of the phalanges ; they are thick in the interspaces of the joints, thin 

 where the tendons lie upon the joints, and they are lined upon their inner 

 surface by synovial membrane. 



LIGAMENTS OF THE LOWER EXTREMITY. 



The ligaments of the lower extremity, like those of the upper, may be 

 arranged in the order of the joints to which they belong ; these are, the 



1. Hip joint. 



2. Kn-ee joint. 



3. Articulation between the tibia and fibula. 



4. Ankle joint. 



5. Articulation of the tarsal bones. 



6. Tarso-metatarsal articulation. 



7. Metatarso-phalangeal articulation. 



8. Articulation of the phalanges. 



1. Hip Joint. The articulation of the head of the femur with the ace- 

 tabulum constitutes an enarthrosis, or ball-and-socket joint. The articulai 

 surfaces are the cup-shaped cavity of the acetabulum and the rounded 

 head of the femur ; the ligaments are Jive in number, viz. 



Capsular, Cotyloid, 



Ilio-femoral, Transverse. 



Teres, 



The capsular ligament (fig. 83, 8) is a strong ligamentous capsule, em- 

 bracing the acetabulum superiorly, and inferiorly the neck of the femur, 

 and connecting the two bones firmly together. It is much thicker upon 

 the upper part of the joint, where more resistance is required, than upon 



