Development can be viewed as a journey over a series of stepping stones that lead to the the major milestones of sitting, crawling, and walking. Each stepping stone represents a new level of skill with greater strength, coordination and balance.
The journey that leads to walking independently takes many months to complete. Infants who are motivated and active work very hard to improve their balance and control at each stage - it takes many hours of practice.
Early supported standing
At 4-5 months infants start to support themselves on their legs when held upright. Most infants will also bend their knees and bounce up and down when held upright. This early supported standing stage helps to stretch out the hips and strengthen the leg muscles. The infant also gets used to taking weight on the feet.
Standing with hand support
From about 8-10 months typically developing infants are able to stand with hand support. Notice that the feet are straight and hip width apart.
Initially their balance is precarious and they topple over easily.
However, with practice their balance improves and they are able to support on one hand and reach with the other. Will is able to keep his balance and hold his trunk and head steady even when he shakes a toy vigorously.
They are also able to bend their knees and reach down to retrieve a toy from the floor. Notice again how the feet are straight and vertically below the knees.
Infants with good movement control also practice bending the knees and sitting down in a controlled fashion. This controlled lowering of the body is very important for strengthening the leg muscles.
Pulling up into standing
Typically developing infants will usually start to pull themselves up into the standing position between the ages of 8-10 months. This standing up movement is repeated many times a day, which strengthens the hip, knee and ankle muscles and improves balance control.
Stepping and cruising
Once an infant has developed good balance in standing, he/she will usually start to walk sideways holding onto furniture.
Standing without support
The next step is to learn to stand and balance without support. This is an important stage - a toddler cannot walk if he or she cannot balance in standing.
Early walking
Typically developing toddlers start to walk independently between the ages of 10-15 months (AIMS data). Toddlers with joint hypermobility (low muscle tone) tend to walk a month or two later.
The first steps involve loosing and regaining balance repeatedly.
Different development
Infants with joint hypermobility and low muscle tone, infants at risk for autism, and premature infants tend to reach the important milestones 2-4 months later than typically developing infants.
There are several important underlying reasons for late achievement of standing and walking milestones:
- muscle weakness and tightness associated with joint hypermobility and low muscle tone;
- lack of experience: cautious infants often avoid challenging tasks and as a result do not put in the hours of practice needed for developing the strength, balance and coordination required for walking;
- difficulties with coordination and motor learning associated with developmental coordination disorder, autism and genetic disorders such as William's syndrome.
Hip muscle tightness
Infants with joint hypermobility, low muscle tone and those born preterm often have some tightness in the muscles that cross over the outside of the hips.
This tightness develops when an infant lies with the legs twisted out at the hips and flat on the cot surface.
Infants with hypermobile hip joints also tend to sit with the legs twisted out and the thighs flat on the floor.
The tendency to abduct the hips can also be seen when the infant lies on the tummy.
How hip muscle tightness affects kneeling and standing
An infant with tightness in the hip abductor muscles tends to keep hip wide apart when kneeling: this position makes pulling up to standing difficult.
The infant with tight hips abductor muscles also stands with the legs wide apart, sometimes with the knees locked into hyperextension.
This position affects the infant's ability to balance, reach sideways and twist the trunk.