Musculoskeletal Effects Of Down Syndrome
Original Editors - Nore Boulpaep
Down syndrome is a chromosomal condition characterised by the presence of an extra copy of genetic material on the 21st chromosome, either in whole (trisomy 21) or part (such as due to translocations).
Effects on the Musculoskeletal System
Reduced Muscle Strength
Bone mass and bone geometry are influenced by growth and muscle development in children and adolescents. This process is further modified by hormonal signals.
Motor function in individuals with Down syndrome is characterised by hypotonia and hyperflexibility, which results in an increased risk of joint dislocation and retarded motor skills.
Hypotonia, decreased muscle tone, has a negative effect on the proprioceptive feedback from muscle and joint sensory structures and can have a detrimental effect on the efficiency of co - contractions and postural reactions.
People with Down syndrome have hyperflexibility, more joint mobility than the average. The increased joint mobility may contribute to the lack of posture control. Together with the failure of co-contraction, it can have a negative impact on joint stability. This joint laxity is found in several parts of the body due to the abnormal collagen found in Down syndrome.
Vitamin D Deficiency
There is a damaging effect of vitamin D insufficiency on musculoskeletal health in children and adolescents during the critical time of bone-mass accrual. Vitamin D is not only essential for normal growth of children, but also for the preservation of the bones. Vitamin D is also important for other functions such as muscle tone, the immune defence and even cancer.
Vitamin D, per oral absorbed through food or created under the influence of sunlight, is a precursor of the hormone 1,25 – dihydroxyvitamin D. The latter stimulates the small intestine absorption and kidney reabsorption of calcium and thus ensures a better bone.
In patients with Down syndrome, risk factors, such as inadequate exposure to sun, inadequate vitamin D intake and malabsorption or increased breakdown of vitamin D that accompanies anticonvulsant therapy, contribute to vitamin D insufficiency. Down syndrome patients usually have osteoporosis and fractures as a result of this deficiency.
The accrual of bone mass during childhood is a key determinant of bone health in adulthood, and a low peak skeletal mass is considered an important risk factor for osteoporosis in adult life.
Multivariate analysis showed that Down syndrome was associated with low Bone mineral density (BMD) of the spine. Lack of physical exercise, low muscle strength, insufficient exposure to the sun, low levels of vitamin D and prolonged use of anticonvulsants are all additional risk factors for low BMD.
Physiotherapy can play a major role in the management of children with DS; through movement and exercise, manual therapy, and education physiotherapists can empower people to take charge of their own health and participate in their treatment. The aim of treatment is to assist people to live as independently as possible 
One goal of physical therapy is to minimise the development of the compensatory movement patterns that children with Down syndrome are prone to develop. Working with their muscles and movements will help children reach some of their motor milestones and will prevent them from developing problems, such as bad trunk posture and gait problems.
Children with Down syndrome typically learn to walk with their feet wide apart, their knees stiff and their feet turned out. They do so because hypotonia, ligamentous laxity and weakness make their legs less stable. Physical therapy should start with teaching the child with Down syndrome the proper standing posture when he is still very young. So, feet positioned under the hips and pointing straight ahead with a slight bend in the knees. With appropriate physical therapy, gait problems can be minimised or avoided.
Children with Down syndrome typically learn to sit with a posterior pelvic tilt, trunk rounded and the head resting back on the shoulders. Physical therapy must teach the child the proper sitting posture by providing support at the proper level even before the child is able to sit independently. Appropriate physical therapy can minimise problems with trunk posture.
It is common for children with DS to be delayed in reaching common milestones such as sitting independently, standing and walking. One of the contributing factors to the delay of these specific milestones is poor balance. It is well known that persons with DS are often considered floppy, clumsy, uncoordinated and have awkward movement patterns due to balance issues. These balance challenges often follow the child into the teen years and sometimes into adulthood 
Evidence for Physiotherapy Intervention
Without physical therapy, a child with Down syndrome could end up having postural, gait and orthopaedic problems later in life from using their muscles incorrectly. They also are at greater risk of joint problems if muscles are not strengthened.The importance of early intervention should be emphasised.
Physical therapy at an early age strengthens the muscles, enabling the children with Down syndrome to keep their body in proper alignment and prevent future health problems
An example of a training program titled "Effects of a community – based progressive resistance training program on muscle performance and physical function in adults with down syndrome: a randomised controlled trial, 2008" aimed to improve muscle strength with progressive resistance training. In conclusion the trail concluded that progressive resistance training is a safe and feasible fitness option that can improve upper-limb muscle endurance in adults with Down syndrome.
Various other studies illustrate also positive effects on motor skills.
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