One leg shorter in a child: measurement, shoe lifts and growth

A difference in leg length is called a limb length discrepancy. If the difference is small and the child is well, monitoring may be all that is needed. Centimetres alone do not determine whether a shoe lift or surgery is appropriate: the cause, walking pattern and remaining growth also matter. [1, 2]

Does a 1 cm difference need treatment?

Not automatically. A small discrepancy may be well tolerated; before treating it, the measurement must be reliable and any symptoms need to be assessed. Differences below 2 cm, without associated deformity, are generally managed without surgery. This does not mean that every difference below 2 cm should be ignored, or that a larger measurement makes surgery inevitable. [1, 3]

A leg that looks shorter in a photograph, or shoes that wear differently, cannot establish the size of a discrepancy.

Bone length and an apparent difference

In a structural discrepancy, the femur, tibia or both differ in length from the opposite side. A functional component may involve pelvic position, restricted joint movement or muscle contractures. Both components can coexist; they do not always fall into separate categories. [2]

Assessment therefore includes the legs, pelvis, spine and movement. A compensatory spinal curve is different from structural scoliosis; a shoe lift cannot be promised to correct every spinal asymmetry. Evidence linking small discrepancies to lower back pain is inconsistent. [1, 3]

How the difference is measured

The clinician observes the child standing and walking, compares joint movement and may place measured blocks beneath the shorter leg. The response of the pelvis and walking pattern helps interpret the difference.

When indicated, dedicated leg X-rays can measure the individual bones and assess associated deformities. The examination and positioning are chosen for the child; families do not need to arrange X-rays themselves before the first assessment. [1, 2]

Previous assessments, existing images and a history of fractures or other limb problems are useful. The predicted difference at the end of growth is an estimate to review over time, not a certain outcome derived from one measurement. [2, 3]

When a shoe lift may help

A shoe lift compensates for the difference while it is worn; it does not lengthen the bone. It may be offered to see whether walking, comfort or function improve. The amount of correction, whether it sits inside or outside the shoe, and follow-up are individual decisions. [1, 2]

Before buying a lift or increasing its height, it is necessary to understand which component it is intended to address. Joint restrictions or postural factors also need assessment. Children with the same measured discrepancy do not necessarily need the same lift. [2, 3]

Will the difference increase as the child grows?

This depends on the cause. Some discrepancies are present from birth; others develop after growth plate damage. Certain fractures in children may also be followed by increased growth of the affected limb. Follow-up therefore considers the pattern over time, as well as fracture healing. [1]

The frequency of reviews and any imaging are individual. Growth plate injuries are discussed separately on the page about physeal fractures.

When surgery is discussed

The predicted difference at the end of growth is considered alongside its cause, deformity, function and the demands of treatment. Epiphysiodesis slows or stops growth at one or more growth plates in the longer leg. Lengthening acts on the shorter leg through a different treatment pathway.

Permanent procedures and techniques using implants have different outcomes and complications. Correction is not guaranteed, and weight-bearing after surgery depends on the procedure and the surgeon's instructions. Further details are available on the page about surgical options for limb length discrepancy. [4, 5]

Sport and the next review

A mild discrepancy does not in itself rule out sport. Advice changes if there is pain, fatigue or functional limitation, or during treatment. A shoe lift does not provide general clearance for every activity.

A stable asymmetry without symptoms can be discussed with the child's doctor at a routine review. If it increases, changes walking or raises questions about an existing lift, a focused assessment is useful. A sudden new limp should not automatically be attributed to a known discrepancy: follow the warning signs for a limping child.

For a planned assessment in Milan, see the Italian guide to the paediatric orthopaedic visit and the Gaetano Pini and CTO locations.

Information note: this information does not replace an individual assessment, diagnosis or prescription. Measurements, lifts, reviews and any treatment are determined for the individual child.