This group of patients have involvement of all four limbs. Intellectual impairment is not uncommon and most subjects are non ambulant.

The main areas of orthopaedic concern relate to the spine, hips and feet where deformity is not uncommon. The ability to sit in a comfortable position is paramount. Hip contractures can develop from an early age and this often leads to subluxation and eventually dislocation. Scoliosis (curvature of the spine) is frequent particularly in association with hip dislocation. Frequent monitoring of children is imperative since hip surgery if performed early can arrest progression. In the earlier stages soft tissue hip releases and bracing may be indicated. In established dislocations hip reconstruction involves femoral and pelvic osteotomies.

Foot fusions (arthrodesis) are appropriate for adolescents with severe deformity who have difficulty in wearing suitable shoes.