THE KNEE JOINT 89 



where the knee shows its greatest antero-posterior dimension the 

 ligament is placed near the middle line of the limb. It is attached 

 superiorly to the back of the radius, and inferiorly is directly continued 

 as the subcarpal or check ligament. Its anterior face is attached to 

 the posterior surfaces of the carpal and metacarpal bones, and it gives 

 support in the intervals between these attachments to the carpal synovia] 

 membranes. Its posterior surface is smooth, and forms the anterior 

 boundary of the fibrous tube at the back of the knee termed the carpal 

 sheath, the synovial membrane of which lines this surface of the 

 ligament. Laterally the anterior and posterior common ligaments 

 blend with the internal and external laterals. 



The external lateral ligament arises in the form of a thick cord from 

 the outer surface of the inferior extremity of the radius, and is attached 

 to the following bones : Cuneiform, unciform, and head of outer small 

 metacarpal. The extensor sufFraginis tendon plays through a canal 

 formed in this ligament. The internal lateral ligament, also very 

 powerful at its origin, arises from the inner surface of the inferior 

 extremity of the radius, and is attached to the scaphoid, magnum, 

 trapezoid, large and inner small metacarpal bones. 



Attention should now be directed to the carpal sheath. This is 

 accommodated in a fibrous tube placed at the back of the knee. The 

 tube is formed anteriorly by the posterior common ligament, externally 

 and slightly posteriorly by the inner surface of the pisiform bone, and 

 the remainder of its posterior boundary and the whole of its inner 

 boundary are formed by a band of fibrous tissue, which runs from the 

 pisiform bone to be attached to the inner surfaces of the carpal bones 

 and the internal lateral ligament. This band corresponds to the annular 

 ligament of the human WTist. There is thus formed a complete tube, 

 and through this tube the tendons of the superficial and deep flexors of 

 the digit play. It also gives passage to a number of vessels and nerves. 

 The synovial sheath which lines the tube extends upwards for a distance 

 of from three to four inches above the knee joint, and downwards to 



M 



