ABSTRACT
An 11-year-old girl with early-onset facioscapulohumeral muscular dystrophy (FSHD) presented with progressive gait disturbance and lumbar hyperlordosis. The motor power of her pelvic extensor muscles was grade 3. Pelvic tilt and hip flexion were markedly increased as determined by gait analysis. This FSHD case is an impressive example of a patient demonstrating the concept that weak pelvic extensor muscles cannot keep the spine upright and balanced. The most important factor in the development of hyperlordosis is the weakness of the pelvic extensor muscles, and the results of gait analysis exquisitely explain the pathophysiology. The patient stands with her spine hyperextended to maintain upright posture by a compensatory mechanism of relatively strong back extensor muscles. Corrective surgery for lumbar hyperlordosis was not considered as it could eliminate the compensatory lumbar hyperextension, thus making the spine of the patient stoop forward through the hip joint during walking, being caused by the weakness of her pelvic extensor muscles.