Sternum deformity—pectus carinatum (outward displacement) or pectus excavatum (inward displacement) —is common, as are joint hyperextensibility (but usually small flexion contractures to the elbows), genu recurvatum (backward curvature of the legs at the knees), pes planus (flat feet), kyphoscoliosis, and diaphragmatic and inguinal hernias.