REGION OF THE KNEE. 



543 



upper edge of the articular surface. The epiphyseal line in the tibia lies rather close 

 to the articular surface, being 1.5 cm. (^ in.) below in adults and less in children; 

 it slopes down in front to embrace the tibial tubercle (see Fig. 554). When 

 the disease encroaches on the epiphyseal line, rather than remove it the affected 

 parts are to be curetted away and the remainder left. In those cases where the 

 knee is much contracted, either enough of the bone must be removed to allow of 

 straightening or the hamstring tendons must be cut ; if this latter is done the external 

 popliteal nerve which runs on the inner posterior surface of the biceps tendon must 

 not be wounded. 



Tuberculous Disease of the Knee-joint. The disease begins usually 

 in the epiphyses adjacent to the joint and involves the joint secondarily. The 

 tibia is more frequently the seat than the femur. The swelling and hypertrophy of 

 the synovial membrane and involvement of the adjacent soft parts obliterate the 

 hollows on each side of the patella and cause a bulging below the patella. The 

 knee looks round and swollen, and the condition was formerly called white swelling 

 from the surface being white in color. If liquid accumulates in the joint it becomes 

 distended and flexed, assuming an angle of 120 de- 

 grees. The patella is raised from the condyles; it 

 ' ' floats ' ' and if depressed by the finger can be felt 

 striking on the femur beneath, thus demonstrating 

 the presence of liquid in the joint. The swelling 

 extends above the patella to an extent depending 

 on whether or not the subfemoral bursa is involved 

 and whether or not it communicates with the joint. 



If pus forms it tends to find an exit beneath the 

 lower edge of the posterior ligament or on either side 

 of the patella at the upper end of the tibia. As the 

 disease progresses the ligaments become weakened. 

 The joint, being already flexed at approximately 1 20 

 degrees, is flexed still more by the hamstring muscles, 

 and the head of the tibia in old cases becomes drawn 

 backward in a position of subluxation (see Fig. 553, 

 page 541). The pull of the biceps tendon while the 

 leg is flexed rotates the leg outward and this position 

 may persist : a condition of knock-knee is also some- 

 times marked. 



The disease is treated conservatively by appa- 

 ratus, but in exceptional cases the lesser operation 

 of erasion or the greater of resection (see above) 

 is done. " 



Knock-knee and Bow-legs. These condi- 

 tions most frequently result from rachitis or paralysis. 

 Bowing inward of the knee is called knock-knee or 

 genu valgum. Bowing outward is called bow-legs or in some instances, when 

 the deformity is in the joint, as when the condyles are unequal in length, genu 

 varum. 



Knock-knee {Genu Valgum}. This condition has its point of bending most 

 marked at the knee-joint. When caused by rickets the joint surfaces are often not 

 much altered and the deformity is produced by a bending of the tibia or femur 

 close to the joint; hence when an osteotomy is performed just above the condyles 

 of the femur the joint is again brought level and resumes its functions normally 

 (Fig. 555). 



When deformities of the foot or the malpositions due to paralyses produce 

 knock-knee, then often a certain amount of flexion and external rotation of the leg 

 coexist with perhaps lengthening of the internal condyle. In these cases osteotomy 

 of the femur must often be supplemented or substituted by suitable apparatus, opera- 

 tions on the foot, etc. 



Bow-legs. This is almost always caused by softening of the bones, as in rickets. 

 The bending occurs in the bones of both the leg and thigh, and the location of the 



FIG. 555. Knock-knee or genu valgum. 



