88 THE SURGICAL ANATOMY OF THE HORSE 



internal lateral. The anterior common ligament is in the form of a 



tough, four-sided, flat sheet, which protects the front of the joint. It 



is attached superiorly to the front of the lower extremity of the 



radius and inferiorly to the upper extremity of the metacarpal bones. 



Its posterior surface gives support to the synovial membranes of the 



transverse joints in the intervals between its attachments to the anterior 



faces of the carpal bones. It should be noticed that this ligament is 



quite loosely applied to the front of the joint, so that in cases of extreme 



flexion of the knee no undue tension is placed upon the ligament. 



Over its anterior face the tendon of the extensor pedis muscle and the 



tendons of the oblique and great extensors of the metacarpus play_ 



These tendons are shown in Plate XXII, and particular attention should 



be given to the relationship which they bear to the joint itself 



It will from the foregoing be gathered that the structures from 



without inwards in front of the knee joint, taken in order, are as 



follows : 



Skin, 



Subcutaneous fascia, 



Annular band of deep fascia. 



Tendons and their sheaths. 



Anterior common ligament. 



Synovial membrane, 



and these structures must be pierced before we get the condition of 

 '- open joint," excepting in cases of small punctured wounds, which may 

 pass between two of the tendons. Most commonly, however, " open 

 joint" is due to the animal stumbling and falling, when the wound is of 

 such a nature that all the structures named are involved. It should, 

 however, be noticed that the appearance of a synovial discharge is not an 

 absolutely diagnostic symptom of " open knee joint," since this discharge 

 may come from the sheaths of the tendons or burs^e, in cases where the 

 anterior common ligament remains intact. 



The posterior common ligament is deeply seated, and at the point 



