Based on morphologic and radiologic
appearances: increased space between the first and second toes, shortening
and clinodactyly of the fourth and fifth toes, and flat feet are the
findings in some patients. Absent or hypoplastic patellae (laterally placed
or dislocated) are typical. Most patients have pelvic abnormalities: absent
ischial ossification at the ischiopubic synchondrosis, infra-acetabular
axe-cut notch, high iliac angles, large femoral heads with narrowed femoral
necks, coxa valga or vara, and hypoplastic lesser trochanters. Patients may
complain of femoropatellar pain syndrome, but symptoms referable to the
pelvic girdle are very rare. Two sporadic cases of SPS associated with
facial dysmorphic features have been reported: one patient had a flattened
nose with prominent forehead, and the other had micrognathia, high-arched
palate, and subglottic stenosis with generalized tracheomalacia; she also
had bilateral talipes equinovarus (clubfeet). These facial and airway
abnormalities likely are not part of the SPS itself. The differential
diagnosis of SPS is either an isolated finding of displaced patellae or the
“nail-patella syndrome” (iliac horns, elbow abnormalities, nail
dystrophy).