Orthopedics - Oleksa A.P. 2006

Congenital and Acquired Deformities of the Lower Extremity
Lower Limb Axis Deviation
Flail Knee Joint

Relaxation of the knee joint (relaxatio genus) most commonly results from previous poliomyelitis, less frequently from inflammatory and destructive Changes in the processes of the Femur or Tibia, and occasionally following traumatic injuries to the bones, their processes, or the Ligamentous apparatus of the knee.

Patients experience constant instability in the knee joint, particularly when walking, due to joint laxity, which severely impairs limb function.

Examination reveals knee deformity and, in a standing position, malalignment of the lower extremity axis. Palpation of the knee is painless. Assessment of the range of motion reveals pathological mobility in the joint beyond physiological norms. Lateral instability is most common, alongside occasional excessive mobility in the sagittal plane caused by cruciate ligament insufficiency.

Radiological changes depend on the underlying Etiology. Following past inflammatory and dystrophic processes, findings include incongruity of the articular surfaces, uneven widening of the joint spaces, and sometimes sequelae of destruction.

Following childhood poliomyelitis, flattening of the articular surfaces may be observed.

Laboratory Blood and urine tests show no deviations from the normal range.

Diagnosis of a flail knee joint is based on the patient's medical history and Clinical presentation.

Treatment aims to restore the static and dynamic function of the lower extremity. Functionally stabilizing orthotic devices are used in children and adolescents, particularly those with a history of poliomyelitis who present with instability in both the knee and ankle joints.

In cases of bilateral lower limb involvement due to poliomyelitis, knee arthrodesis is sometimes performed on one leg, while brace fixation is used on the other.

Arthrodesis is advisable in adulthood for patients engaged in physical labor who present with a unilateral flail knee joint, whereas joint replacement (arthroplasty) may be performed in others.

Patients are eligible for vocational placement and disability status determination.



Last update: 10/08/2026

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