PRACTICAL CONSIDERATIONS : THE KNEE-JOINT. 



415 



bones, as would be the case if the axis of the whole lower limb were a perpendicular 

 running through the acetabulum and the centre of the ankle-joint, but by the help 

 of muscular and ligamentous structures. 



The tendency (which is so common a factor in the production of deformities) 

 to assume an attitude which will transfer strain from a tired muscle to the neighboring 

 ligaments operates here to cause stretching and elongation of the internal lateral 

 ligament, as the "attitude of rest" with the feet separated and everted is the one 

 usually adopted. The evil effects are, of course, favored by much standing, and are 

 most marked in young persons of feeble physique whose weight has increased dis- 

 proportionately to their muscular strength. The outer side of the knee shows the 

 changes due to increased pressure and to long-continued approximation of musculo- 

 tendinous points of origin and insertion, — i.e., atrophy of the outer condyle and 

 outer tuberosity ; contraction and shortening of the ilio-tibial band of fascia, of the 

 external lateral ligament, of the tendon of the biceps, and of the tensor vaginae 

 femoris. The inner side shows the effects of removal of normal pressure from grow- 

 ing bones and of chronic strain of fibrous and periosteal tissue, — i.e., overgrowth of 

 the femoral diaphysis just above the inner end of the epiphyseal line and of the tibial 

 diaphysis just below the corresponding level ; lengthening of the internal lateral 

 ligament ; bony outgrowth at its tibial insertion from chronic periostitis. 



The tibia is apt to be rotated outward, possibly through the action of the short- 

 ened biceps. Talipes valgus (^. v. ) may be either a cause or a result of genu valgum. 

 The disappearance of the deformity when the knees are flexed 

 is probably due to the outward rotation of the femur that ac- 

 companies flexion, and not, as is generally stated, to the fact 

 that the antero-posterior diameter of the condyles is unaffected 

 by the disease. * 



The clinical symptoms and results and the treatment by 

 apparatus cannot be described here. 



In Maceweyi' s osteotomy the femur is divided from the inner 

 side of the thigh at a point twelve millimetres (half an inch) 

 above the adductor tubercle and in a line at right angles to 

 the long axis of the femur. Osteotomy may also be done from 

 the outside of the thigh and at the same level. These opera- 

 tions are usually safe, but the popliteal artery, the anastomotica 

 magna, the external peroneal nerve, and other important struc- 

 tures have been accidentally divided. 



Genu vafiim — " bow-leg" — is almost always rhachitic in its 

 origin. A child with rickets and having lumbar lordosis of the 

 spine stands with its thighs slightly flexed, either as a secondary 

 result of the shortening of the ilio-femoral ligaments produced 

 by backward rotation of the pelvis (to compensate for the for- 

 ward rotation of the sacrum ) or more simply as an easy method 

 of relaxing the weak ilio-psoas muscles and preserving the 

 centre of gravity. As the thighs flex the knees separate, the 

 femurs rotate outward on their own axes, the line of gravity 

 falls to the inside of the centre of the knee-joint (Fig. 428), the 



pressure is greatest on the inner condyle and tuberosity, the strain comes upon the 

 external lateral ligament, and the outward bowing begins and is continued by the 

 leverage of the body weight. 



Genu recurvatum — " back-knee" — is a deformity in which, as a result of intra- 

 uterine malposition, or of congenital paralysis of the flexors and popliteus, or of 

 pressure brought upon the posterior and crucial ligaments in walking in a case of 

 partial paralysis of the quadriceps,— the limb being swung forward, the heel coming 

 to the ground in full extension, and the weight of the body reaching the joint in 

 front of its centre of gravity, — the knee is bent backward and the whole limb presents 

 a long curve with its concavity forward. 



In excision of the knee the lines of the epiphysis should be remembered if the 

 patient is under twenty or twenty-one years of age (page 365), the relation of the 

 femoral vessels to the posterior ligament, the situation and extent of the synovial 



Showing the form of the 

 bones in bow-legs. 



