Congenital Dislocation of the knee is rare and may occur due
to a contracture of the quadriceps. This condition usually occurs in patients
with myelo, arthrogryposis, or Larsen’s syndrome. The patient with a congenital
dislocation of the knee may have developmental dysplasia of the hip (DDH) and
club foot. On examination, the patient will have a hyperextended knee at birth.
They may have their foot placed against their face and there will be limited
flexion at the knee. The patient may have a dimple or skin crease at the
anterior aspect of the knee. You must examine the hip to rule out ipsilateral
hip dislocation. 50% or more patients will have hip dysplasia. The etiology is
not known; however, it could be due to fetal positioning or congenital absence
of the cruciate.
There are grades, or a spectrum, for this deformity. Grade I
deformities are referred to as Severe Genu Recurvatum, and the knee is
hyperextended. If the range of passive flexion is more than 90°, it is
considered to be a simple recurvatum. Grade II deformities are identified by
subluxation with a range of 30-90° in passive flexion. Grade III deformities
are complete dislocations with a range of passive flexion being less than 30°.
Congenital dislocation of the knee will take priority over
treatment of hip dysplasia or club foot. The Pavlik harness and club foot cast
will require knee flexion, so the physician will need to treat the knee
dislocation first. With Grade I deformities, the initial treatment will be
stretching of the knee and serial casting with the knee in flexion. In serial
stretching and casting, the goal is to obtain at least 90° of flexion and
reduction of the deformity over the course of several weeks. The physician
should avoid pseudo-correction through an iatrogenic fracture of the proximal
tibial physis. The prognosis is usually good if reduction is achieved without
surgery. With Grade II deformities, if the infant is less than 1 month old, you
will do serial casting first followed by percutaneous quadriceps recession,
especially if the flexion is less than 90°. In Grade III deformities, a V-Y
quadricepsplasty with above the knee cast is done in Grade III (frank dislocation),
especially if nonsurgical treatment fails to reduce the tibia on the femur. The
result of open surgery is better when it is done in children younger than 6
months. In general, open reduction is reserved for children who did not respond
to stretching and cast immobilization. It is important that the hip dysplasia
is recognized and the knee dislocation is corrected early. This will help in
early reduction of the hip.
