The answer is D. Obligate external rotation and abduction of the hip with passive flexion
The expected finding is obligate external rotation and abduction of the hip as it is passively flexed — the Drehmann sign. Flex the affected hip toward 90 degrees and the thigh will not stay in neutral; it rolls out into external rotation and abduction on its own. It is a mechanical consequence of the anatomy: the femoral epiphysis stays seated in the acetabulum while the metaphysis displaces anteriorly and rotates externally, so the only path the femur has through flexion is out and away. The companion findings are limited internal rotation, abduction, and flexion, with pain reproduced on passive internal rotation, and an antalgic or Trendelenburg gait.
The single highest-yield clinical fact about SCFE is that the pain is often felt in the knee. Referred pain along the obturator nerve distribution sends adolescents to clinic complaining about a knee that examines completely normally, and the hip is never examined — which is why the average diagnostic delay is measured in months and why so many slips progress from stable to unstable before anyone images them. Adolescent knee or thigh pain with a normal knee examination requires a hip examination and hip radiographs.
The epidemiology fits this patient exactly: SCFE is the most common hip disorder of adolescence, peaking around ages 10 to 16 in boys and 10 to 14 in girls, disproportionately in children with obesity, because mechanical shear across a physis that is already widened and weakened by the pubertal growth spurt is what causes the slip. When a slip appears in an unusually young, thin, or short child, screen for an underlying endocrinopathy — hypothyroidism, growth hormone deficiency, panhypopituitarism, or renal osteodystrophy. Imaging is bilateral hip radiographs with anteroposterior and frog-leg lateral views; the frog-leg lateral shows the posteroinferior displacement best, and on the AP view Klein’s line — drawn along the superior femoral neck — fails to intersect the epiphysis. Image both hips, because up to a third slip on the other side.
Management is immediate non-weight-bearing and urgent orthopedic referral for in-situ percutaneous screw fixation. Do not attempt reduction; forceful manipulation raises the risk of avascular necrosis, which along with chondrolysis is the feared complication. Classify the slip as stable or unstable by whether the child can bear weight, because unstable slips carry a far higher rate of osteonecrosis.
Sorting the distractors: a positive Ortolani sign — a palpable clunk as a dislocated femoral head reduces into the acetabulum on abduction — is a finding of developmental dysplasia of the hip in a neonate, not an adolescent; increased internal rotation is the opposite of what happens, since the displaced metaphysis specifically limits internal rotation; a positive Galeazzi sign, in which the knees sit at unequal heights with the hips and knees flexed, again indicates developmental dysplasia or true limb-length discrepancy in a young child; and a palpable snap over the greater trochanter is external snapping hip syndrome from the iliotibial band flicking across the trochanter — a painless or mildly painful mechanical phenomenon in an active adolescent, without the antalgic gait and rotational restriction seen here.
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