Paediatric Musculoskeletal Development

Original Editor - Robin Tacchetti based on the course by Krista Eskay
Top Contributors - Robin Tacchetti, Jess Bell and Naomi O'Reilly

Introduction

The musculoskeletal system is influenced by many different factors as infants and children grow. It can adapt to the demands, or lack of demands, that are placed on it. The major load on bone comes from muscle forces. When muscle pull is altered due to genetic or neuromuscular conditions, alignment may be impacted. Atypical alignment can directly affect functional activities and an individual's participation.

The following sections highlight key stages and changes that occur during musculoskeletal development.

Rib Cage

• Initially, the rib cage in infants is barrel-shaped and rigid; ribs are elevated and perpendicular to the spine
• By 2 years, the rib cage is oblong-shaped; the ribs depress and develop an angulation in relation to their attachment with the spine - this is due to the diaphragm pull and forces from sitting/standing/walking; there is also lateral expansion of ribs (caused by breathing, the action of intercostal muscles, gravity)
• Atypical = persistence of the barrel shape

Trunk

• Initially, infants have a kyphotic spine
• Overtime this transitions to a more "neutral" spine (as seen in adults)
• Specific activities which encourage this transition:
  • Prone push-ups and sitting activate the posterior chain musculature (i.e. the infant is pushing into thoracic extension)
  • Crawling creates co-contraction of the anterior and posterior muscles (for stability)

Changes in Alignment to Consider

Increased Curvature of the Spine

Increased curvature of the spine (i.e. scoliosis) can affect:

• breathing
• lung positioning
• heart location
• visceral function

Pelvis

• Initially, infants have a rounded pelvis with a posterior tilt
• Sitting and standing activate core muscles, which leads to the development of an anterior pelvic tilt
  • At 12 months old: an infant has 12 degrees of anterior pelvic tilt
  • At 30 months old: a child has 15 degrees of anterior tilt
  • Anterior tilt decreases to around adult angles (i.e. around 10 degrees) by age 8

Lower Extremities

Typical joint patterns in infants are as follows:

• Hip: flexion, abduction and lateral rotation
• Knee: flexion, genu varum, medial rotation of tibia
• Ankle: dorsiflexion, slight pronation

These joints are discussed in more detail below.

Hip

Infants are born with:

• increased hip external rotation which decreases over time
• hip adduction limitation
• 34 degrees of hip extension limitation
  • as infants spend more time in prone, their anterior capsule stretches, decreasing the hip extension limitation
    • 
      at 6 weeks old infants have a 19 degree hip extension limitation
    • toddlers have a 7 degree hip extension limitation
• increased coxa valga - 140-160 degrees
  • as become more ambulatory, femoral neck angle decreases
  • decreases over time to 126 degrees in adults

• anteversion of the femur - 40 degrees
  • this decreases to 16 degrees in adults

Changes in Alignment to Consider (Hip and Pelvis)

Hip

• Femoral neck angle remains high - high femoral anteversion: increased risk of posterior hip dislocation
• Please note that it is especially important to consider the hips in children who are non-ambulatory at the age of 30 months

Increased Anterior Pelvic Tilt

• Abdominals and hip extensors are long
• Hip flexors and lumbar extensors are short
• Leads to difficulty activating abdominals and gluteus muscles, which can make it difficult for children to engage in functional play / activities

Decreased Anterior Pelvic Tilt

• Iliopsoas and anterior hip capsule are long / stretched out
• Gluteus maximus is shortened
• Leads to anterior hip laxity and hip instability

Pelvic Obliquity

• Common in individuals with hemiplegia and diplegia
• Depressed hip side (shorter side):
  • shorter, lower extremity or increased pronation on this side
  • reduced stance time
  • reduced loading, resulting in less bony deposition, so the long bones of this leg tend to grow at a slower rate
  • sometimes functional ankle plantarflexion (i.e. so can reach the ground with this foot)
• Longer side:
  • often have compensatory foot pronation
  • there may be medial rotation of the lower extremity and knee flexion to compensate
• Leads to gait asymmetry, pelvic rotation on the shorter side
• Significant increase in pelvic obliquity might contribute to:
  • imbalances in sitting
  • pain due to "impingement of the pelvis on the ribs"
  • ischial decubitus / pressure ulcers

Knee

• Genu varum
  • infants born in genu varum (i.e. bow-legged position)
  • by toddlerhood, knees are in genu valgum (i.e. knock-knee position) - genu valgum peaks around 2 1/2 years old and then decreases over time
  • by adulthood, knee should be in neutral
    
• Knee flexion
  • infants born with 30 degree knee flexion contracture
  • resolves in the first few months of life
• Infants are born with medial rotation of the tibia
  • this resolves by 12 months

Changes in Alignment to Consider

Increased Medial Tibial Torsion

• Internal rotation of the tibia
• Not common
• Toeing in
• Most likely associated with medial rotation occurring higher up in the chain

Increased Lateral Tibial Torsion

• External rotation of the tibia

• Individuals present with crouched posture

Increased Genu Valgum

Possible impairments:

• pain in calf, thigh and/or knee
• increased fatigue with activities
• less efficient gait
  • decreased gait velocity
  • decreased balance
• increased Q-angle
  • quadriceps less efficient secondary to abnormal muscle pull
• lateral subluxation of the patella
• collapse of the medial foot arch
• protective in-toeing

Ankles/Feet

Infants are born with:

• hindfoot varus
  • with weight bearing, transitions to valgus
• feet straight forward or slight pointing in
  • toeing out increases in adults
• high arch
  • adults tend to transition to flatter feet

Role of Paediatric Physiotherapy

Physiotherapists can help facilitate correct movement patterns to improve biomechanical alignment. Early intervention is associated with better functional outcomes. Some interventions that paediatric physiotherapists use are listed below:

• weight shifts
• loading
• static positioning devices
• splinting
• bracing

The video below by Pathways demonstrates a 2-month-old typical vs. atypical development side by side:

Resources

• Biomechanics
• Infant Development
• Coxa Vara / Coxa Valga
• Valgus Knee