Genu recurvatum is defined as hyperextension of the knee beyond 180° or the zero reference position. In most cases, it is bilateral, symmetrical, constitutional in origin, and asymptomatic. It can be congenital or acquired (bony, ligamentous, or mixed), and in the latter case, asymmetrical and possibly symptomatic. It presents with various clinical manifestations: pain, femorotibial instability, patellofemoral instability, leg length discrepancy, and even cosmetic concerns. The physical examination should be thorough and, above all, comparative bilateral.

Radiographic examination allows measurement of the degree of recurvatum, both in the intra-articular or extra-articular bony aspect and in the ligamentous aspect. Bony recurvatum is distinct from ligamentous recurvatum, but they can be associated. Etiological investigation allows selection of the appropriate treatment.

Anterior tibial opening osteotomy techniques predominate in surgical treatment, but they are not the only ones. Ligamentous or conservative procedures can also be performed, either in conjunction with or in isolation.

Genu recurvatum can be congenital, constitutional, or acquired. Most often, it corresponds to a common physiological condition in adults. In this case, it contributes to the correct locking of the knee in daily life and can be essential for final acceleration in a sprint. There is a consensus that symmetrical recurvatum should be preserved. Symmetry here refers to the similarity between both legs.

In contrast, acquired genu recurvatum is usually asymmetrical and symptomatic, and should be considered pathological. Furthermore, genu recurvatum greater than 20° is considered excessive. In these cases, surgical correction should be considered.

Genu recurvatum is defined by the degree of hyperextension of the knee beyond the sagittal femorotibial alignment of 180° or the reference position (0°). A femorotibial angle of 190° corresponds to a global recurvatum of 10°.

Three types of genu recurvatum are distinguished.

This refers to constitutional or familial genu recurvatum, normally less than 15°. In a reference population of 100 people, Lecuire et al. found knee hyperextensions of 0-5° in 11% of cases, 5-10° in 21%, and 10-15° in 8%. If found incidentally or as a result of an aesthetic evaluation, it does not require any special treatment. However, beyond 15°, or in the presence of symptoms, surgical treatment may be necessary.

Congenital genu recurvatum: Genu recurvatum is much less frequent and more severe. It is often associated with arthrogryposis (congenital dislocation of the knee due to a complex malformation of the joint). Most of the time, it requires surgical treatment.

Acquired genu recurvatum is the consequence, for example, of a distal femur fracture or a proximal tibia fracture healed with malunion, or of muscle weakness secondary to paralysis. The cause may be bone-related or ligamentous. In the clinical and radiological study, the overall genu recurvatum is measured, and the bone component (femoral or tibial) is evaluated, followed by the ligamentous component in cases of mixed recurvatum.