tand without the aid of a crutch, or when weight is put on
the limb, it assumes the attitude of genu recurvatum. The usefulness
of the limb may be improved by the application of a rigid apparatus
with a lock at the joint so that it can be used in the extended
position for walking or in the flexed position for sitting. The rigid
knee produced by arthrodesis affords good support but is inconvenient
in sitting.

When the _quadriceps alone_ is paralysed, the patient is obliged to
maintain the joint in the position of extreme extension, because the
least degree of flexion results in the limb giving way under him. In
course of time the posterior ligament is stretched, and the joint
becomes hyper-extended, acquiring the attitude of _genu recurvatum_.
When it is bilateral the gait is seriously impaired. The treatment
consists in applying an apparatus which prevents hyper-extension, in
improving the condition of the thigh muscles, and in wearing a splint
at night which secures the flexed position. Recourse may be had to
operative measures, such as transplanting one of the hamstrings into
the patella, so as to compensate for the loss of power in the
quadriceps, arthrodesis, or supra-condylar osteotomy of the femur.

When the quadriceps is overcome by a _contraction of the hamstrings_,
as in spastic paraplegia, the knee is fixed in the flexed position and
the child is unable to walk. The flexion may be corrected by
lengthening the hamstring tendons, bringing the divided biceps tendon
through an opening in the vastus lateralis, and attaching it to the
rectus and to the patella. If there is a combination of flexion and
genu valgum, the knee-joint should be resected and ankylosed in the
straight position.

#Contracture and Ankylosis at the Knee.#--In addition to the different
paralytic forms above described, contracture may result from
ulceration and suppuration in the popliteal space, and from disease
(osteomyelitis) in one of the adjacent bones. The greater number of
contractures and ankyloses are the result of disease in the joint, and
have already been described.

GENU VALGUM AND GENU VARUM

In the normal limb, a line drawn from the centre of the head of the
femur to a point midway between the malleoli passes through the
centre of the knee-joint. If the line passes outside the centre of the
knee-joint, the condition is one of genu valgum; if inside, it is one
of genu varum (Fig. 135).

[Illustration: FIG. 135.]

#Genu