PRACTICAL CONSIDERATIONS : THE KNEE. 



645 



of the compact tissue of the shaft with the cancellated tissue of the expanded lower 

 extremity. It is from one to two inches higher than the epiphyseal line. The same 

 backward rotation of the lower fragment occurs as in disjunction of the epiphysis 

 (page 365), and in both cases from the action of the gastrocnemius. In the fracture, 

 however, the sharp lower end of the upper fragment is far more apt to project ante- 

 riorly than is the diaphysis in cases of epiphyseal disjunction. It is not infrequently 

 entangled in fibres of the rectus and may lacerate the suprapatellar synovial pouch. 

 The difference probably results from the character of the fracturing force, which in the 

 epiphyseal accident is, in the majority of cases, hyperextension of the leg on the 

 thigh. The action of the ilio-psoas tends to advance the lower end of the upper 

 fragment, but must be feeble. The pectineus slightly and the adductors quite strongly 

 draw it inward. The shortening is produced by the hamstrings, rectus, sartorius, 

 etc. The. most difficult element of the deformity to do away with is the posterior 

 rotation of the lower fragment, which may also result in serious pressure upon or 

 injury to the popliteal vessels and nerves. In setting such a fracture it may be neces- 

 sary to relax the chief muscles concerned by liexing the thigh to a right angle with 



Fig. 614. 



Fig. 615. 



Upper 

 fragment 



Vastus- 

 externus 



riiacus 

 Psoas major 



Lower fragment V' f ;y. 

 Popliteal artery — 



Lower 

 fragment 



Adductor 

 muscles 



Gastrocnemius, 

 outer head 



Patella 



Tibia 



Gastrocnemius, 

 inner head 



Dissection of fracture of upper third of right femur, 

 showing forward and inward displacement. 



Dissection of fracture of lower third of left femur, show- 

 ing displacement of popliteal artery by lower fragment. 



the pelvis to relax the ilio-psoas, drawing the knee inward a little to relax the ad- 

 ductors, and flexing the leg on the thigh to relax the gastrocnemius, and then to 

 make extension by means of the forearm placed in the ham. Not uncommonly the 

 displacement recurs so obstinately that it becomes necessary 'to treat the case with 

 the leg fully flexed on the thigh, and even to divide the tendo Achillis. 



3. The Knee.— The skin over the front of the knee is dense, coarse, and 

 loose, quahties that diminish the gravity of the frequent injuries to the integument 

 itself and also serve to protect the underlying joint, ' ' especially in stabs with bluntish 

 instruments" (Treves) and, in fact, in many forms of accident in which the free 

 movement of the skin over the subjacent structures serves to make the application of 

 force to the latter much less direct. 



In full flexion the skin, in spite of its laxity, is drawn tensely over the patella, 

 and a fall may result in an extensive wound. 



The relation of the cutaneous nerves and vessels over the knee to those supply- 

 ing the articulation should be studied in connection with the common application of 

 counterirritants or of blisters to the region. 



