The syndrome of diminished femoral antetorsion, evaluated in 111 joints of 59 children and adults, is described. Internal rotation of the femur was significantly decreased, and external rotation was increased. Femoral antetorsion was diminished in biplane radiographs to an 8.5 degrees mean value [1.0 degree in computed tomography (CT) scans]. Antetorsion values are higher in children, even in this syndrome. Pain was mainly experienced between the ages of 12 and 30 years. Ten patients had signs of beginning osteoarthritis. Rotational osteotomies performed to increase antetorsion were successful.