Leg alignment refers to whether the legs are straight or not.
Normal development of the legs involves the following changes:
Bow-leg (varus) in the infant which then aligns to straight legs by around 18 months and then into a knock-knee (valgus) around 3-4 years. Straight leg (adult alignment) is present by around 7 years.
These changes are usually mild and should not cause limp or discomfort.
The figure below demonstrates the normal changes of alignment at different ages
More information about bow-legs, knock-knees are available.
Typically normal variants of alignment will be asymptomatic (cause no discomfort) and be symmetrical. In children where there are other medical concerns or asymmetry between the legs, other pathologies should be considered.
Indications for concern and referral are available.
The photograph below shows severe knock knee abnormality - this is asymmetrical and extreme and therefore not a normal variant.