THE HOCK JOINT rii 



quality, so that through it could be seen a reddened and roughened 

 surface of bone for nearly the whole length of the inner lip of the 

 trochlea. The patella was unaltered except that the articular cartilage 

 corresponding to the diseased part of the femur was thin. 



"The second case occurred in a black mare about eight years old, 

 which had done three years' work. The history of the lameness was the 

 same as in the other case — at first not well-marked, chiefly stiffness. 

 Then came the ' wooden ' position of the hind limbs, for both were 

 affected — the difficulty of movement when made to walk, and the 

 striking rigidity of the extensor muscles of the thigh, especially the 

 vastus externus and the tensor vagince femoris. 



" The post-mortem examination disclosed just the same lesions as in 

 the first case. 



" These symptoms and lesions are entirely different from those found 

 in the more common stifle-joint lameness known as ' Gonitis.' In the 

 latter disease there is usually synovial distension, the lesions are on the 

 articular head of the tibia, and the condyles of the femur, whilst during 

 life a common attitude is to hold the affected limb, so that the foot is 

 carried forward and raised from the ground." 



THE HOCK JOINT 



This is a joint of great importance since it is the seat of some of 

 the most serious and troublesome affections with which surgeons have 

 to deal. 



It is a composite joint and consists of a number of articulations. 

 The most important is that formed between the distal end of the 

 tibia, and the astragalus. This is a joint of the ginglymoid variety and 

 in it most of the movement of the hock joint takes place. The remain- 

 ing joints are restricted to a simple gliding or arthrodial movement. 



The articular surfaces of the tibio-astragaloid or true hock joint 



