354 CHAPTER 47. 



tendons belonging to tne muscles. For instance in the knee, the extensor 

 inetacai'pi tendon runs over the anterior portion of the joint. These 

 tendons, it is necessary to bear in mind, are furnished with synovial 

 sheaths. 



716. True open Joint. 



True open joint is always marked by the emission of synovia, more 

 commonly called joint oil, from the wound. 



It does not however follow, that the joint is really laid open, because 

 there is an emission of synovia from the wound. Synovia, though in less 

 quantity, will be emitted, if the sheath of any tendon, which passes over 

 the joint, is cut through. 



If the synovia proceeds only from the sheath of a tendon, the case will 

 probably be neither very serious nor very tedious. If on the other hand 

 the joint is laid open, there is more danger. It is never advisable to 

 explore the wound. Much more injury than good generally results from 

 any such over-anxiety to ascertain the extent of the injury. 



All synovial joints are liable to be laid open by external injuries ; but 

 the knee for various reasons, which will readily occur to the reader, is far 

 more apt to suffer than any other joint. Principally for this reason, the 

 author proposes to dwell somewhat fully on injuries of the knee, and but 

 slightly on injuries of other true joints. The general principles of treat- 

 ment are much the same, whichever be the joint injured. The minor 

 differences, arising from difference in position of the various joints, and 

 from the nature of the injuries to which they are respectively most 

 liable, will be noticed hereafter. 



717. Broken knee. 



Broken knee is a term used somewhat indiscriminately by the public 

 to express any injury of the knee, whether it be a mere abrasion of the 

 skin, or hair, or a more serious injury, or the true joint be laid open. 



We have spoken of the knee hitherto as a true joint, but in reality it 

 consists of three true joints. The different layers of bones form three 

 distinct articulations. Each layer or apposition of bones is furnished 

 with its own capsular ligament. A wound perforating the so-called joint 

 may occur in any of these articulations. Practically, however, we find, 

 that it generally occurs in either of the upper articulations and but rarely 

 in the lowest one. 



Non-professional men are apt to think, that the injury occurs in the 

 lowest articulation, because the exterior wound generally appears to be 

 low down. This, however, is caused by a difference in the position of 

 the skin, when the knee is bent and when it is straightened. It is the 

 upper part of the knee, which usually conies in contact with the ground. 



The knee, we may remark, corresponds anatomically with the wrist, 

 not with the knee in the human subject. 



