The Impact SMA Can Have On The Spine, Hips And Bones

Because SMA causes muscles to get weaker, people with SMA can have problems with the bones that are supported by the muscles (orthopaedic problems). SMA can weaken the muscles that support the spine which, without this support, can be pulled by gravity and curve. It’s estimated that as they grow, 60-90% of non-sitters and sitters develop a spinal curvature, as do 50% of walkers. When the spine curves sideways into a “C” or “S” shape it’s called a scoliosis. When the spine bends forward it's called a kyphosis. At the same time as the spine curves, there are changes to the chest wall and rib cage which reduce the space available for the lungs to grow and for breathing. 

Weakening muscles can also mean that some people who are sitters and walkers have ‘unstable hips’. How much muscles weaken and what effect this has on anyone’s spine and hips day to day is very individual - no two people are the same. 

Another thing that can be an issue for people who are non-sitters and sitters is not being able to use bones and muscles as much as someone who can walk. Standing has several benefits for health (see section on Posture, Movement & Exercise) but if you’re a non-sitter you won’t be able to stand and if you’re a sitter you’ll find it hard work to stand for a long time, even with support. This makes you more at risk of bone fractures due to what’s called osteoporosis (when bones are weaker and more likely to break). 

Page last reviewed: August 2021

Next review: August 2022