9.1 Gross Motor Development and Developmental Milestones
Key Takeaways
Interpret milestone windows alongside symmetry, movement quality, progression and caregiver observations. Use corrected age as appropriate after preterm birth.
Describe early reflexes in context. Persistent obligatory posture, marked asymmetry or loss of skill warrants a broader developmental assessment.
Righting aligns the head and trunk. Protective extension adds support and equilibrium responses help recover balance. Record the direction and conditions of testing.
Early walking often has short, wide, variable steps. Interpret foot contact in relation to walking experience and the broader examination.
AIMS observes infant gross motor development, PDMS-3 provides norm-referenced gross and fine motor results, and GMFM measures changes in gross motor capacity using edition-specific procedures.
Gross Motor Development and Developmental Milestones
Infants develop head, trunk and limb control through changes in strength, coordination and experience. Head and trunk stability often support later skills such as reaching and walking. Observe spontaneous movements, variability and symmetry across different positions. Ask caregivers how the child moves and participates at home.
Chronological Timeline of Gross Motor Milestones
Milestones help track change over time. The WHO Motor Development Study estimated these overlapping windows from the 1st to the 99th percentile in its reference population.
| Observed skill | WHO reference window |
|---|---|
| Sits without support | 3.8–9.2 months |
| Stands with assistance | 4.8–11.4 months |
| Crawls on hands and knees | 5.2–13.5 months |
| Walks with assistance | 5.9–13.7 months |
| Stands alone | 6.9–16.9 months |
| Walks alone | 8.2–17.6 months |
Some children in the WHO cohort skipped hands-and-knees crawling. Saudi MOH well-child visits include assessment of developmental skills and referral when delays or developmental concerns are identified. Use movement quality and the pattern over time alongside the age windows. Loss of a skill, marked asymmetry, or significant parent concern warrants evaluation even within a reference window.
Corrected age example: An infant born at 32 weeks was born 8 weeks before 40 weeks. At 24 weeks chronological age, corrected age is weeks. Use corrected age for developmental follow-up after preterm birth through about 2 years, following the local protocol and the selected instrument’s instructions.
Kinematic Hallmarks of Early vs. Mature Walking
New walkers often take short, wide, variable steps and may hold their arms up for balance. Initial foot contact can vary between steps. Studies following new walkers show changes in foot contact and roll-over as experience increases. Steps generally become longer, narrower and more consistent with practice.
Ask how long the child has walked independently. Compare the sides and watch starts, stops, turns and transitions. A recently learned gait can look less consistent than that of a child the same age with more practice. Look for changes over time, and assess persistent asymmetry, pain or loss of walking.
Primitive Reflexes
Early infant reflexes are automatic responses elicited under particular examination conditions. Their expression changes with age, state and position. Interpret them with spontaneous movement, tone, symmetry, feeding and developmental history.
| Response | What to observe |
|---|---|
| Moro | With the infant supported and using a standardized maneuver, a brief change in head position can elicit arm abduction and extension followed by adduction and flexion. Compare sides. |
| Asymmetrical tonic neck response (ATNR) | Head turning can elicit extension on the face side and flexion on the opposite side, often most evident in the arms. Record whether the posture is brief or sustained and whether the infant can move out of it. |
| Symmetrical tonic neck response (STNR) | In a described quadruped test, neck flexion is associated with arm flexion and leg extension, with the reverse pattern on neck extension. Document the observed response in context. |
| Tonic labyrinthine pattern (TLR) | Position relative to gravity can influence flexor or extensor posture. The response is described in infant reflex profiles. Consider the spontaneous movement pattern and the rest of the neurological assessment. |
| Palmar and plantar grasp | Pressure in the palm can elicit finger flexion. Pressure under the toe bases can elicit toe flexion. The responses decline on different timelines. |
| Rooting and sucking | Cheek stimulation can elicit head turning and mouth opening. Sucking and swallowing are coordinated feeding behaviors and are assessed separately when feeding is a concern. |
Longitudinal studies show variation in early responses. For example, plantar grasp can still be present after 6 months. A sustained obligatory posture, marked asymmetry, unusually limited movement or abnormal tone warrants a broader neurological and developmental assessment. Early cerebral palsy pathways use age-appropriate standardized tools, such as General Movements Assessment in younger high-risk infants and the Hammersmith Infant Neurological Examination (HINE) in later infancy, with imaging where indicated. Arrange timely referral when findings raise concern.
Postural Reactions: Righting, Protection, and Equilibrium
Righting reactions help align the head and trunk with gravity and the environment. For example, an infant may orient the head as the trunk tilts, drawing on visual, vestibular and somatosensory cues.
Protective extension adds support by extending an arm or both arms toward the support surface. In sitting, look for a hand placed forward, toward the side of a lateral displacement, or behind the pelvis during a backward displacement. Observe the direction, symmetry and amount of support. The forward parachute item in the HINE uses a supported forward tilt and its own age-based scoring. Use the manual for administration and interpretation. Seated propping and the suspended parachute response are different examination tasks.
Equilibrium responses use changes in trunk and limb position to manage a change in support or body position. Compare the infant’s ability to recover balance in the positions they can safely attempt. The response depends on the task and available support.
Worked example: A 7-month-old sits without support and props forward and sideways but does not consistently prop backward. Record each response and the testing setup. Backward propping can still be developing. Check symmetry, spontaneous sitting and transitions, and reassess with the wider developmental picture.
Standardized Pediatric Assessment Tools
Choose the measure by age, purpose and scoring instructions. An observational infant measure, a norm-referenced motor test and a measure of change in gross motor capacity answer different clinical questions.
1. Peabody Developmental Motor Scales
The current PDMS-3 assesses gross and fine motor development from birth through 5 years 11 months. The core subtests are Body Control, Body Transport, Object Control, Hand Manipulation and Eye–Hand Coordination. Physical Fitness is supplemental. In older records, PDMS-2 has a different structure, including Reflexes, Stationary, Locomotion, Object Manipulation, Grasping and Visual–Motor Integration. Use the specified edition's procedures, norms and scores.
2. Alberta Infant Motor Scale (AIMS)
The AIMS observes gross motor development from birth through 18 months or independent walking. It has 58 items across prone (21), supine (9), sitting (12) and standing (16). In each position identify the span from the least to the most mature item observed. Credit items below that span and observed items within it according to the scoring instructions. Convert the total to a percentile using the appropriate age.
In one high-risk cohort, Darrah and colleagues identified the 10th percentile at 4 months adjusted age and the 5th at 8 months as the best predictive cutoffs in that study. Interpret a low score with risk history, serial observations and the rest of the examination.
3. Gross Motor Function Measure (GMFM)
The GMFM is a criterion-referenced measure of change in gross motor capacity. The GMFM-88 has five dimensions: lying and rolling, sitting, crawling and kneeling, standing, and walking, running and jumping. It has validity evidence in cerebral palsy and Down syndrome, and its procedures can accommodate assessment with shoes, orthoses or mobility aids when clinically appropriate. Record the conditions so later scores can be compared.
The GMFM-66 provides an interval-scaled total for children with cerebral palsy using Rasch-calibrated items and the Gross Motor Ability Estimator or the developer's GMFM App+. Follow the edition-specific procedure, including testing conditions. For a child with cerebral palsy being followed after selective dorsal rhizotomy, use the same version and comparable conditions across visits to quantify change.
A 7-month-old infant turns the head to the right and repeatedly shows sustained right arm and leg extension with left-sided flexion. The infant has difficulty moving out of the posture. What is the most appropriate interpretation?
The pattern resembles an obligatory asymmetric tonic neck response and warrants a broader developmental and neurologic evaluation
This is the normal emergence of a symmetric tonic neck response and needs no additional assessment
The movement demonstrates a typical protective extension response to falling backward
This is a normal isolated walking milestone
A 7-month-old who recently began sitting independently props forward and to the side but does not consistently extend an arm behind the body during a guarded backward sitting displacement. What is the best documentation?
Diagnose severe equilibrium dysfunction from the absent response
Document each directional response and reassess with other findings because backward propping may still be developing
Record absence of forward parachute even though only the backward sitting response was inconsistent
Diagnose a persistent Moro response from the observed pattern
A physical therapist wants to quantify change in gross motor capacity in a 6-year-old with cerebral palsy after selective dorsal rhizotomy. Which measure provides a Rasch-scaled gross motor score for this purpose?
Peabody Developmental Motor Scales, Third Edition (PDMS-3)
Alberta Infant Motor Scale (AIMS)
Gross Motor Function Measure (GMFM-66)
Gross Motor Function Classification System (GMFCS)
A 13-month-old who has walked independently for two weeks takes short steps with a wide base. Which additional observation can be consistent with this walking experience?
A fixed one-sided gait pattern that has become progressively more pronounced
New loss of the ability to bear weight on one leg
A new loss of independent walking after previously doing it consistently
Variable initial foot contact and raised arms during walking
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