The distal femoral physis accounts for 40% of the longitudinal growth of the lower extremity, growing approximately 9 mm per year until skeletal maturity.

Morphologically, this growth plate is not flat but instead has undulations across its surface which add to the stability of the physis but also make it more prone to damage when fractures of the physis occur.

The medial and lateral collateral ligaments originate from the distal femoral epiphysis distal to the physis. The anterior and posterior cruciate ligaments originate from the intercondylar notch, also distal to the physis (FIG 2).

The popliteal artery courses along the posterior surface of the distal femur as its traverses the popliteal space. The sciatic nerve divides into the peroneal and posterior tibial branches just proximal to the physis. Anterior displacement of the distal fragment is associated with popliteal artery injury, and medial displacement is associated with peroneal nerve injury.

Physeal fractures generally cleave through the zone of hypertrophic calcification then go either proximal (SH I and II) or distal to this zone (SH III and IV). In distal femoral physeal fractures, however, the fracture cleaves not only through the hypertrophic zone but also crosses other zones including the germinal zone of the growth plate because of its undulating morphology, making growth disturbance likely even after SH I and II fractures.

These fractures result most commonly from medial or lateral forces applied to the knee, resulting in varus (medial) or valgus (lateral) displacement, respectively.

Knee hyperextension injuries lead to anteriorly displaced fractures while direct forces applied to the flexed knee, such as a dashboard strike during a motor vehicle crash, commonly cause intra-articular SH III and IV fractures.

The distal femoral physis has tremendous healing and remodeling potential in children with at least 2 years of growth remaining. In this age group, fractures with anatomic realignment of the joint surface that are realigned with less than 10 degrees of deformity in the anteroposterior (AP) and lateral planes heal with restoration of normal function in most patients who do not develop a growth arrest.

For patients who develop a growth arrest, however, the results are variable. The growth disturbance is the result of either injury to the germinal cells of the physis from the trauma of the initial injury or subsequent reduction, from malreduction with physeal bar formation, or from iatrogenic injury from screws that cross the physis.^{1, 2, 6}

The resulting problems related to growth disturbance are angular deformities from incomplete arrest or limb length discrepancy from complete physeal closure.

Because of the high risk of growth-related problems, patients and their families must be counseled at the time of initial treatment about the potential for complications.

High-quality AP and lateral radiographs of the entire extremity are necessary to fully assess these injuries as well as the overall alignment of the limb and other associated fractures (FIG 3). Dedicated views of the knee, with comparison views of the uninjured side if necessary, are useful to precisely define the fracture pattern, especially when the fracture is nondisplaced.

Computed tomography (CT) of the knee is indicated for most intra-articular fractures (SH types III and IV) to define the fracture pattern and the degree of displacement as well as to aid in planning of fixation (FIG 4).⁵

Magnetic resonance imaging (MRI) is used to confirm occult fractures when the radiographs are normal but the examination is suspicious for a fracture as well as to diagnose other knee pathology such as meniscus tears, ligament tears, and osteochondral injuries.⁴