134 THE SURGICAL ANATOMY OF THE HORSE 



THE STRAIGHT LIGAMENTS OF THE PATELLA 



These three ligaments attach the patella to the anterior tuberosity 

 of the tibia. The external is the largest and is also the most powerful, 

 but owing to its position it is most exposed to risk of injury and is 

 occasionally ruptured, rupture in this case being due usually to violence, 

 such as a blow or poke received from some projecting portion of a 

 vehicle such as a shaft during a collision. Rupture of one or other, 

 or both, of the remaining ligaments may be caused by some extra- 

 ordinary and sudden effort on the part of the crural muscles the action 

 of which, it will be remembered, is transmitted to the limb through 

 the medium of the straight patellar ligaments. 



When rupture of one or more ligaments occurs the animal is 

 disinclined to place weight on the affected limb owing to the natural 

 resistance to the action of the extensors of the stifle. The patella is 

 kept in position on the trochlea by the fixed condition of these 

 muscles. Diagnosis is best made by palpation and manipulation. 

 The ligaments which remain intact may be located without much 

 difficulty, but over the seat of the ruptured ligament a depression 

 will be felt. Prognosis is usually favourable. Absolute rest should be 

 provided, and after about ten to fourteen days a mild counter-irritant 

 applied. 



Beneath the lower portion or the middle straight ligament, and near 

 its insertion into the anterior tibial tuberosity, is a small synovial bursa, 

 which sometimes becomes enlarged owing to an abnormal accumula- 

 tion of its synovial contents. At times the affection is of a dropsical 

 nature and occasions no pain or interference with the limb. Most 

 frequently, however, it is a bursitis, as a result of a blow received over 

 the front of the stifle. The swelling which arises may be detected 

 without much difficulty and appears in the depression which is normally 

 present below the patella. The quadriceps muscles are relaxed, and 



