Congenital Dislocation of the Knee: Idiopathic or Arthrogryposis?

Fetal akinesia associated with fixed joints is a common cause for suspicion of arthrogryposis multiplex congenita, a severe condition with heterogeneous etiology. We present the case of a rarer but more benign condition, congenital knee dislocation. The authors report the case of a 27-year-old woman medicated with levetiracetam for epilepsy whose prenatal ultrasound at 22 weeks of gestational age revealed bilateral clubfoot, permanent extension of the inferior limbs with internal knee rotation, normal amniotic fluid quantity, and fetal echocardiography. The remaining ultrasounds revealed similar results. Prenatal genetic testing revealed no pathological findings. The pregnancy was otherwise uneventful. A female newborn was delivered at 39 weeks by cesarean section, with no need for resuscitation. She presented with bilateral knee hyperextension and clubfoot, spontaneous movements, and normal mobility in all other joints. The remaining physical examination and brain and hip ultrasound on the second day of life were normal. These findings were compatible with idiopathic congenital dislocation of the knee (CDK). The patient was undergoing treatment with favorable evolution and adequate neurodevelopment, at the time of this report.  This case describes a diagnostic workup with the exclusion of severe syndromic pathologies, namely arthrogryposis. Despite the initial suspicion of arthrogryposis, a condition with a poor prognosis, this infant presented a more benign disease with favorable evolution.