PRACTICAL CONSIDERATIONS : THE KNEE-JOINT. 



413 



upon the thigh. This is aided in dorsal decubitus by gravitation, which also 

 favors the outward rotation of the leg that commonly occurs at the same time. 



The swelling of synovitis, whether acute or chronic, is limited, until the capsule 

 gives way, by the attachments of the synovial membrane, — that is, it extends upward 

 beneath the rectus for from two to three finger-breadths or from four to five centi- 

 metres (one and a half to two inches) above the summit of the patella ; laterally, it 

 reaches the same level under the vastus internus, but is not quite so high on the 

 other side, under the vastus externus. Downward, it descends to nearly the middle 

 of the ligamentum patellae, attaining the same level on the inner side, but stopping 



Fig. 426. 



Tendon of extensor quadriceps 

 uprapatellar bursa 



Cavity of joint 



Patella 



External condyle—. 



— Prepatellar bursa 



External lateral ligament 



Tendon of popliteus 

 Popliteal bursa- 



Head of fibula-i 



External semilunar 

 cartilage 



Ligamentum patellae 



Subpatellar bursa 



-Tubercle of tibia 



Tibia 



Right knee-joint. The joint-cavity and several bursae have been distended with injection mass before dissection. 



(Spalteholz.) 



just above the head of the fibula on the outer side. The patella is separated from 

 the trochlea of the femur — " floated up." In testing for this symptom, it is impor- 

 tant to grasp the anterior muscles of the thigh firmly and draw them towards the 

 knee so as to relax the pull of the quadriceps, which is occasionally great enough to 

 hold the patella in contact with the femur, even in the presence of considerable 

 effusion (Fig. 426). 



The condition is usually unmistakable, but may have to be differentiated from 

 periarticular abscess or haematoma. In the latter cases the swelling will not be 

 uniform ; the inner depression at the side of the patella may be obliterated, and not 



