Down Syndrome (Trisomy 21): Physiotherapy Management & Motor Development

Down Syndrome (DS) is the most common chromosomal cause of intellectual disability. Children with DS present with a distinct motor profile characterized by hypotonia and ligamentous laxity. While they eventually achieve most gross motor milestones, they do so with delay and often develop compensatory movement patterns. This guide covers the specific musculoskeletal features, safety red flags, and evidence-based PT interventions.

1. The Musculoskeletal Profile

Children with DS are not just "delayed"; they have physiological differences that affect how they move.

• Generalized Hypotonia: Low muscle tone (floppy), making it harder to generate force and maintain posture against gravity.
• Ligamentous Laxity: Hyperflexible joints (double-jointedness) leading to instability, flat feet (pes planus), and hip instability.
• Short Limbs: Shorter arms/legs relative to the trunk affect leverage during movement (e.g., sitting balance is harder).
• Poor Balance: Delayed development of righting and equilibrium reactions.

2. Critical Safety: Atlanto-Axial Instability (AAI)

⚠️ RED FLAG: Cervical Spine Instability
Up to 15-20% of children with DS have instability between C1 and C2 vertebrae due to lax ligaments. While often asymptomatic, it poses a risk of spinal cord compression.

Screening: X-rays are often done around age 3-5, but clinical vigilance is key. Avoid excessive neck flexion/extension activities (e.g., somersaults) until cleared.

Signs of Cord Compression (Immediate Referral):

• Change in gait (clumsiness, spasticity).
• Neck pain or torticollis (head tilt).
• Weakness in hands/arms.
• Bladder/bowel changes.

3. Motor Milestones: Typical vs. Down Syndrome

Expect delay. The goal is progress, not matching the "typical" timeline perfectly.

Milestone	Typical Age Range	Down Syndrome Average
Sitting alone	5 – 9 months	6 – 30 months (Avg: 11 mo)
Crawling	6 – 12 months	8 – 22 months (Avg: 17 mo)
Standing alone	8 – 17 months	1 – 3.5 years
Walking alone	9 – 18 months	1 – 4 years (Avg: 24 mo)

4. Physiotherapy Interventions

A. Early Intervention (Birth to 3 years)

• Tummy Time: Essential to strengthen neck extensors against hypotonia. Use a wedge or therapy ball if too difficult on the floor.
• Handling: Teach parents to carry the child in ways that promote "tucking in" (flexion) rather than letting limbs dangle.
• Postural Control: Support the trunk to allow hand use. Prevent "W-Sitting" (which they love due to laxity) as it harms hip development.

B. Treadmill Training (Evidence-Based)

Research (Ulrich et al.) shows that high-intensity, supported treadmill training helps infants with DS walk months earlier than standard care.

• Start when the child can sit alone (approx 10 months).
• Use parent support for trunk.
• 8-10 minutes daily.

C. Orthotics (SMOs)

Because of severe pronation (flat feet) and ankle instability, Supramalleolar Orthoses (SMOs) are the gold standard.

• Purpose: Stabilize the heel (calcaneus), support the arch, and provide a stable base for standing balance.
• Timing: Usually prescribed when the child begins to pull-to-stand or cruise.

5. Revision Notes for Students

Pathology: Trisomy 21 (extra chromosome).
Key Motor Features: Hypotonia + Ligament Laxity.
Safety #1: Atlanto-Axial Instability (C1-C2). Avoid somersaults/neck strain.
Gait Pattern: Wide base, out-toeing, pronated feet, stiff knees (to rely on ligaments rather than muscle).
Best Intervention: Treadmill training for gait; SMOs for foot alignment.
Cardiac: 40-50% have congenital heart defects (ASD/VSD)—monitor endurance.

6. FAQs for Parents

Q1. Will my child be able to walk?

Yes. The vast majority of children with Down Syndrome will walk. It just takes longer (average 24 months). Some may walk as early as 18 months, others by age 4.

Q2. Why does my child stick their tongue out?

This is due to a small oral cavity and relative macroglossia (large tongue), combined with low tone in the jaw/mouth muscles. Oromotor therapy can help.

Q3. Should I force them to stop W-sitting?

Yes, gently correct it. W-sitting relies on joint structures rather than muscle for stability. It can lead to hip dislocation and knee strain in the long term. Encourage "tailor sitting" (criss-cross) or long sitting.

7. 10 Practice MCQs

Q1. The most common orthopedic concern requiring screening in Down Syndrome is:

Answer: B) C1-C2 instability poses a risk of spinal cord injury.

Q2. Which type of muscle tone is characteristic of Down Syndrome?

Answer: C) Generalized low muscle tone ("floppy").

Q3. Which orthosis is most commonly prescribed for children with DS who are beginning to stand?

Answer: B) SMOs control the severe pronation/eversion while allowing some ankle motion.

Q4. W-sitting should be discouraged because:

Answer: B) It provides passive stability, preventing the child from developing trunk control.

Q5. On average, children with DS achieve independent walking by:

Answer: C) While the range is wide, 2 years is a common average.

Q6. Which intervention has strong evidence for accelerating walking onset in DS?

Answer: B) Supported treadmill walking stimulates the stepping pattern generator.

Q7. Ligamentous laxity in DS often results in:

Answer: B) The ligaments cannot support the arch, leading to collapse (pronation).

Q8. A common compensatory strategy for standing balance in DS is:

Answer: B) Locking the knees relies on ligaments for stability ("hanging on their ligaments") due to muscle weakness.

Q9. Approximately what percentage of children with DS have congenital heart defects?

Answer: B) PTs must monitor endurance and signs of cardiac distress.

Q10. A sign of spinal cord compression from AAI includes:

Answer: C) Neurological regression or neck symptoms warrant immediate medical review.

References

• Tecklin, J. S. (2015). Pediatric Physical Therapy. Lippincott Williams & Wilkins.
• Ulrich, D. A., et al. (2001). Treadmill training of infants with Down syndrome. Physical Therapy.
• National Down Syndrome Society. (2020). Therapies & Development.