Knock-Knee 479 



nerve, the superficial part of the anastomotica magna, and .the long 

 saphenous vein. (The origin of the poplitetis is within the joint.) 



Knock-knee. In the erect posture the tibiag are vertical, with 

 their heads close together ; but the heads of the femora are separated by 

 the width of the pelvis. The wider the pelvis the greater the separa- 

 tion of the femora above, and the greater the inward slant of the bones 

 to the knee. All of us, then, are a little ' in-kneed,' and women parti- 

 cularly so. So that the lower surfaces of the condyles may be on the 

 same level, the inner condyle must be the longer. Nevertheless, it is 

 not so prominent anteriorly as is the outer (p. 449). In a weakly, rickety 

 subject the internal lateral ligament is apt to stretch, over-growth of 

 the internal condyle consequently taking place, for some of the pressure 

 of the tibia against it is lost. Eventually the deformity becomes per- 

 manent. 1 



As the rectus femoris follows the axis of the femur, whilst the liga- 

 mentum patellae follows that of the tibia, when the muscle contracts it 

 is apt to drag the knee-cap over the external condyle ; outward dis- 

 location would happen still more often were it not for the presence of 

 that prominent flange limiting the trochlear surface externally. 



In estimating- the amount of knock-knee the joint must be 

 completely extended, so that the lateral ligaments may be tightened 

 and the tibia firmly locked on the femur, for when these ligaments are 

 at all slack a little lateral and rotatory movement is enough to efface 

 the defect. 



Operation for knock-knee has to be performed when gentler 

 methods cannot avail. In a young child forcible straightening often 

 succeeds without any cutting. In this operation the knee must be 

 first extended to the utmost so as to prevent rotation of the tibia as 

 the surgeon exerts his strength. It is not known exactly what occurs 

 in this process : perhaps the external lateral ligament yields a little ; 

 perhaps the inner femoral condyle undergoes some condensation ; 

 perhaps the epiphysis is slightly separated from the diaphysis on the 

 outer side. It is, however, a satisfactory procedure. 



Ogston sliced off the inner condyle of the femur, and then, by 

 bringing the leg straight, shifted the loosened condyle upwards until 

 the lower surfaces of the condyles were on the same level. One great 

 disadvantage of this original operation was that, the knee-joint being 

 implicated, suppuration or stiffness was apt to ensue. 



To obviate this risk, MacEwen partially divides the shaft of the 

 femur above the internal condyle, and completes the operation by 

 forcible fracture. He draws a transverse line a finger's breadth above 

 the external condyle, and a vertical one half an inch in front of the tendon 

 of the adductor magnus. At the meeting of these lines he makes 

 a small vertical incision on to the femur and introduces his osteotome, 

 which he then turns across the length of the femur, cutting the bone 



1 For 'Anatomy of genu valgum ' see Journal of Anat. and Phys. 1879. 



