In certain malformations of the lower lhbs it is necessary to intervene surgically to make it possible for the child to walk, or to improve its walking ability. Surgical intervention is camed out at an appropriate stage in the child's development and in close co-operation with the prosthetist and orthotist. Longitudinal deficiency tibia, total or partial Orthopaedic-surgical treatment cannot be avoided if a child with this condition is to walk. If possible the operation is carried out at the suckling age, so that walking can start according to the child's development. If, in the case of longitudinal deficiency tibia total, the femoral condyles and the knee capsule are normal, and if the child is to be operated on not later than in his second year of life, the Brown (1965) procedure-that is the construction of a knee joint between the femoral condyles and the head of the fibula-is indicated. During a second operating session the distal end of the fibula is fused with the astragalus or calcaneus according to Blauth (1978) in preference to disarticulation of the ankle joint. From the third year of life, disarticulation of the knee joint is the method of choice if the tibia is totally lacking and a normal femur is present. If the distal femur is hypoplastic, there may be a more or less serious disturbance of the growth and, after a knee disarticulation, a cone shaped, eventually mid-thigh and poor load carrying stump end. In such a case, especially if malformations of the upper limbs are present, fusion between the condyles of the femur and the head of the fibula is recommended; also between