#Separation of the lower epiphysis# is a comparatively common injury. It is seldom pure, a portion of the diaphysis usually being broken off and remaining attached to the epiphysis. It occurs usually in boys between the ages of thirteen and eighteen, from severe violence such as results from the limb being caught between the spokes of a revolving wheel, or from hyper-extension of the knee. It has also been produced in attempting forcibly to rectify knock-knee and other deformities in this region, and in making traction on the limb to correct deformities following recovery from tuberculous disease of the knee. As a rule, there is little displacement of the loose epiphysis, but it may pass in any direction, forward being much the most common (Fig. 82), and when displaced it is difficult to reduce and to maintain in position. The age of the patient, the mode of injury, the finding of the smooth broad end of the diaphysis in the popliteal space or on the front of the thigh, according to the displacement, usually serve to establish the diagnosis. The X-rays afford reliable information as to the position of the fragments. Pressure on the popliteal vessels is a serious aggravation of the injury, and adds greatly to the difficulties of treatment. [Illustration: FIG. 82.--Radiogram of Separation of Lower Epiphysis of Femur, with backward displacement of the diaphysis; pressure on popliteal vessels caused sloughing of calf.] [Illustration: FIG. 83.--Separation of Lower Epiphysis of Femur, with fracture of lower end of diaphysis.] The treatment is the same as for supra-condylar fracture, but, owing to the serious disability that follows on incomplete reduction, it may be necessary to have recourse to operation. After an epiphysial separation, the growth of the limb is sometimes, although not always, interfered with. #Either condyle# may be broken off without the continuity of the shaft being interrupted, by a direct blow or fall on the knee, or by violent twisting of the leg. The separated condyle may not be displaced, or it may be pushed upwards or rotated on its transverse axis. There is broadening of the knee but no shortening of the thigh, and the ecchymosis, crepitus, and pain are localised to the affected side of the joint; the knee can usually be moved towards the injured side in a way that is characteristic. If allowed to unite with the condyle displaced, the articular surface is oblique and bow- or knock-knee results. If there is difficulty in replacing the broken condyle and maintaining it in position, it may be fixed by means of a steel nail inserted through the skin. FRACTURE OF THE UPPER END OF THE TIBIA