Knock-Knee And Bow-Legs

These conditions 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, operations on the foot, etc.


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 point of greatest bending is sometimes low down toward the ankles or close up to the knee-joint, or the whole diaphysis of the bones may be curved. They are often curved anteroposteriorly as well as laterally (Fig. 556).

Fig. 555.   Knock knee or genu valgum.

Fig. 555. - Knock-knee or genu valgum.

When the point of greatest bending is close to the knee-joint it has been called genu varum, but the condyles remain of equal length and the epiphyseal line still remains parallel with the joint line.

As knock-knees and bow-legs so commonly occur in the actively growing period, from the second to the fifth year, apparatus is often of benefit, but frequently forcible straightening by means of an osteoclast or by the hand or epiphysiolysis (see page 542) or osteotomy is resorted to for their correction.


In osteotomy of the femur the bone is to be divided, as advised by Macewen, a finger-breadth, at least, above the adductor tubercle and 1.25 cm. (1/2 in.) in front of the adductor magnus tendon. In knock-knee many surgeons prefer dividing the bone from the outside of the limb instead of the inside as advised by Macewen. This incision avoids the epiphyseal line, which is opposite the adductor tubercle, and also the anastomotica magna and superior articular arteries. The popliteal vessels are also to be avoided by knowing their position and not directing the osteotome toward them. In performing osteotomy of the bones of the leg the tibia is to be divided by the aid of the chisel, and the fibula is to be broken by manual force. Wedge-shaped resections of bone are commonly not to be advised. They are difficult to do, liable to complications, and, under the most favorable circumstances, are very long in healing and do not give any better results than simple osteotomy or osteoclasis. Ligation of the Popliteal Artery. - In the middle of its course the popliteal artery lies deep between the condyles of the femur and on the posterior capsule and gives off the articular arteries. For these reasons ligation in this part of its course is not performed. To ligate it in the upper part of its course an incision is to be made along the outer edge of the semimembranosus muscle near the middle of the upper part of the popliteal space. The muscle being drawn inward the internal popliteal nerve is first seen and drawn outward, then the vein beneath is also drawn outward and the artery found beneath and a little to the inner side. Don't mistake the semitendinosus for the semimembranosus. The former is a round tendon, the latter is muscular. Another method consists in making the incision immediately behind the adductor magnus tendon. The semimembranosus and semitendinosus are then to be drawn backward and the artery located by its pulsation and the aneurism needle passed from within out. The nerve and vein, being more to the outer side, are not disturbed (Fig. 557).

To ligate the popliteal artery in its lower third, make an incision in the midline between the heads of the gastrocnemius muscle, avoiding the short saphenous vein and nerve. Open the deep fascia, draw the internal popliteal nerve to the inner side, the popliteal vein to the outer side, and pass the needle from without in. Flexing the knee will relax the gastrocnemius and enable the artery to be more readily exposed.