BOW-LEG (Genu Varum), a deformity characterized by separation of the knees when the ankles are in contact. Usually there is an outward curvature of both femur and tibia, with at times an interior bend of the latter bone. At birth all children are more or less bandy-legged. The child lies on its nurse's knee with the soles of the feet facing one another; the tibiae and femora are curved outwards; and, if the limbs are extended, although the ankles are in contact, there is a distinct space between the knee-joints. During the first year of life a gradual change takes place. The knee-joints approach one another; the femora slope downwards and inwards towards the knee-joints; the tibiae become straight; and the sole of the foot faces almost directly downwards. While these changes are occurring, the bones, which at first consist principally of cartilage, are gradually becoming ossified, and in a normal child by the time it begins to walk the lower limbs are prepared, both by their general direction and by the rigidity of the bones which form them, to support the weight of the body. If, however, the child attempts either as the result of imitation or from encouragement to walk before the normal bandy condition had passed off, the result will necessarily be either an arrest in the development of the limbs or an increase of the bandy condition. If the child is weakly, either rachitic or suffering from any ailment which prevents the due ossification of the bones, or is improperly fed, the bandy condition may remain persistent. Thus the chief cause of this deformity is rickets (q.v.). The remaining causes are occupation, especially that of a jockey, and traumatism, the condition being very likely to supervene after accidents involving the condyles of the femur. In the rickety form the most important thing is to treat the constitutional disease, at the same time instructing the mother never to place the child on its feet. In many cases this is quite sufficient in itself to effect a cure, but matters can be hastened somewhat by applying splints. When in older patients the deformity arises either from traumatism or occupation, the only treatment is that of operation.
A far commoner deformity than the preceding is that known as knock-knee (or Genu Valgum). In this condition there is close approximation of the knees with more or less separation of the feet, the patient being unable to bring the feet together when standing. Occasionally only one limb may be affected, but the double form is the more common. There are two varieties of this deformity: (i.) that due to rickets and occurring in young children (the rachitic form), and (ii.) that met with in adolescents and known as the static form. In young children it is practically always due to rickets, and the constitutional disease must be most rigorously dealt with. It is, however, especially in these cases that cod-liver oil is to be avoided, since it increases the body weight and so may do harm rather than good. The child if quite young must be kept in bed, and the limbs manipulated several times a day. Where the child is a little older and it is more difficult to keep him off his feet, long splints should be applied from the axilla or waist to a point several inches below the level of the foot. It is only by making the splints sufficiently long that a naturally active child can be kept at rest. The little patient should live in the open air as much as possible.
The static form of Genu Valgum usually occurs in young adolescents, especially in anaemic nurse-girls, young bricklayers, and young people who have outgrown their strength, yet have to carry heavy weights. Normally in the erect posture the weight of the body is passed through the outer condyle of the femur rather than the inner, and this latter is lengthened to keep the plane of the knee-joint horizontal. This throws considerable strain on the internal lateral ligament of the knee-joint, and after standing of long duration or with undue weight the muscles of the inner side of the limb also become over-fatigued. Thus the ligament gradually becomes stretched, giving the knee undue mobility from side to side. If the condition be not attended to, the outer condyle becomes gradually atrophied, owing to the increased weight transmitted through it, and the inner condyle becomes lengthened. These changes are the direct outcome of a general law, namely, that diminished pressure results in increased growth, increased pressure in diminished growth. The best example of the former principle is the rapid growth that takes place in the child that is confined to bed during a prolonged illness. The distorted, stunted, shortened and fashionable foot of the Chinese lady is an example of the latter. Flat-foot (see Club-Foot) and lateral curvature of the spine, scoliosis, are often associated with this form of Genu Valgum, the former being due to relaxation of ligaments, the latter being compensatory where the deformity only affects one leg, though often found merely in association with the more common bilateral variety. In the early stages of the static form attention to general health, massage and change of air, will often effect a cure. But in the more aggravated forms an apparatus is needed. This usually consists of an outside iron rod, jointed at the knee, attached above to a pelvic band and below to the heel of the boot. By the gradual tightening of padded straps passing round the limbs the bones can be drawn by degrees into a more natural position. But if the patient has reached such an age that the deformity is fixed, then the only remedy is that of operation.