SYNOVITIS OF THE KNEE. 131 



most marked in those instances in which the (so-called) ligamen- 

 tum teres is diseased, for the obturator nerve sends a special 

 branch into the substance of this structure. 



It is possible also that pain from inflammation of the anterior 

 part of the hip may be even referred, through the internal 

 saphenous nerve, to the inner side of the ankle, and also that 

 pain may be felt in the heel or foot owing to the fact that the 

 twigs supplying the posterior part of the hip- joint and the nerve 

 fibres constituting the great sciatic and its divisions are all derived 

 from the same source, namely the sacral plexus. It is well to 

 bear in mind however that pain referred to these various places 

 is by no means always present in morbus coxae, and because of 

 its absence inflammation of the hip must not be overlooked. 



In suppurative synovitis (arthritis), the purulent material as a 

 rule perforates the capsule posteriorly where it is thinnest, and 

 gives rise to an abscess behind. Subsequently, however, the pus, 

 following the line of least resistance, tracks forward beneath the 

 gluteus minimus and medius, and at the anterior border of these 

 muscles it passes internal to the tensor fasciae femoris and deep 

 to the upper part of the sartorius, forming a swelling in the 

 upper and outer part of Scarpa's triangle. 



When the acetabulum is perforated, as it may readily be in 

 children in whom the Y-shaped cartilage is still in existence, pus 

 will collect within the pelvis between the bones and the obturator 

 internus. Hence a rectal examination should not be neglected in 

 any case of suppuration in connection with the hip-joint. 



Knee-joint. Probably synovitis of the knee-joint occurs almost 

 more frequently than inflammation of any other joint except the 

 ankle. The synovial cavity of the knee-joint is the largest in the 

 body and yet it only requires an ounce and a half to two ounces 

 of fluid to completely distend it in the normal adult articulation. 



The limits of the synovial cavity are readily seen when fluid is 

 poured out as the result of inflammation. All the natural de- 

 pressions around the joint are obliterated, and elevations appear 

 in place of them. Thus, bulging will be seen on either side of 

 the highest part of the ligamentum patellae and laterally to the 



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