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Knee Dislocation (Genu Recurvatum)
KEY POINTS
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Hyperextension of the leg with dislocation at the knee may result from the legs being in an extended posture with breech presentation, oligohydramnios, or other unusual late gestational constraint, and it can also occur in various genetic connective tissue disorders.
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If the tibia is displaced anterior to the long axis of the femur, the knee is considered dislocated , but if longitudinal contact is at least partially maintained, it is subluxed .
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Treatment depends on the severity of the knee dislocation and the age when treatment begins, with early conservative treatment consisting of serial casting and traction.
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Because congenital hip dislocation is often associated with congenital knee dislocation, it is important to evaluate the hips sonographically, because the dislocated knee needs to be reduced before the hip dislocation is treated.
GENESIS
Hyperextension of the leg with dislocation at the knee may result from the legs being in an extended posture with breech presentation, oligohydramnios, or other unusual late gestational constraint caused by uterine myomas or structural defects. It can also occur in various genetic connective tissue disorders, such as Ehlers-Danlos syndrome, Larsen syndrome, and related FLNB disorders, or certain neurological disorders such as arthrogryposis or PIK3CA -related overgrowth spectrum. Dislocation of the hips is frequently associated with congenital knee dislocation, and this combination is much more common in females, especially when there is no associated syndrome. It is frequently associated with other musculoskeletal problems, especially dislocation of the hip and clubfoot, so it is prudent to search for an underlying disorder, such as Larsen syndrome or arthrogryposis. In a fetus at 22 weeks with bilateral clubfoot, fixed extension of the lower limbs, and internal knee rotation, it can be difficult to distinguish congenital knee dislocation from arthrogryposis.
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