Structural and functional leg length differences should be distinguished. Measurement, heel lifts and insole needs require individual assessment; a pressure map does not measure bone length.
Leg length discrepancy describes a difference in the length of the lower limbs or an apparent difference when standing. Feeling that one leg is shorter does not always mean the bones are genuinely different lengths. Before selecting a heel lift, the source of the difference and its effect on daily movement need assessment.
Small differences may cause no symptoms in some people. In other circumstances, walking, standing or comfort during activity may be affected. Rather than relying only on a measurement, assessment considers age, symptoms, previous injuries and whether growth is continuing.
A structural discrepancy involves a real difference in bone length. The thighbone or shinbone may contribute. Congenital conditions, problems affecting a growth plate and changes following a fracture are possible causes. Previous operations are also relevant to the history.
With a functional or apparent difference, limb position and joint movement matter. Pelvic position, restricted joint movement or postural adaptations may contribute to one leg appearing shorter. Structural and functional components can coexist; looking in a mirror cannot establish the distinction.
This matters because every apparent short leg does not call for the same lift used in the same way. Assessment should consider joint movement and gait as well as the possibility of support beneath the foot.
A noticeable limp, a tendency to load one side or difficulty on longer walks may be observed. Children may compensate by keeping a knee bent or walking on the toes on one side. These signs alone do not diagnose a leg length discrepancy.
Back, hip and knee pain can also have other causes. Finding a difference in leg length does not establish that it explains every symptom. Uneven shoe wear alone cannot prove which leg is shorter either. The onset of symptoms and their relationship to movement should be considered alongside examination findings.
Assessment usually begins with a history and physical examination. A clinician may ask about fractures, operations, childhood growth problems and current symptoms. Standing posture, walking and joint movement are examined. Positioning and the anatomical landmarks used affect how a measurement is interpreted.
During a standing block test, measured blocks are placed beneath the side thought to be shorter while pelvic level is assessed. This helps clinical evaluation, but it is not automatically a precise measurement of individual bone lengths. Where appropriate, a clinician may request standing long-leg radiographs or other suitable imaging.
| Method | Information provided and limitations |
|---|---|
| History and physical examination | Helps assess possible causes, posture and restricted movement. |
| Standing block test | Provides information about pelvic level under load and a clinical estimate of the difference. |
| Appropriate imaging | Can clarify bone lengths and lower-limb alignment when needed. |
| Gait or pressure assessment | Adds information about movement and loading; does not directly measure bone length. |
Home tape measurements, comparing heels in a photograph or estimating millimetres from a phone image are not sufficient for selecting lift height. A coloured pressure map should not be used by itself to claim that one leg is a specific amount shorter. For additional context on gait and loading, see our guide to gait analysis.
A heel lift is a support placed beneath the heel inside a shoe when appropriate. Its aim is to help accommodate the effects of a discrepancy according to an identified need. Neither the side nor the height should be chosen simply because one leg feels shorter.
Immediately compensating for the entire measured difference is not a universal rule. A plan should consider the cause, joint movement, symptoms and shoe fit. Comfort, walking and new pressure areas need monitoring during use. This article does not provide an individual millimetre recommendation or number of layers to add.
A heel lift primarily adds height beneath the heel. An insole may have other aims, such as supporting the foot, cushioning or reducing pressure in particular areas, depending on its design. Not every insole is made to accommodate a leg length difference, and not every soft heel pad functions as a measured lift.
In some circumstances, a lift can be incorporated into an insole plan. If shoe space is insufficient or another arrangement is needed, an external sole raise may be considered. These options are not interchangeable; height and footwear modification need professional planning. Supports do not lengthen the bones. They aim to accommodate the effects of the difference while being worn. You can also review general differences in our guide to orthopedic insoles and material options in our article on silicone insoles.
Adding support takes up shoe space and can change how the heel sits. Footwear needs to hold the foot securely, allow enough toe room and have an appropriate fastening. Bring everyday shoes and any existing inserts to a fitting.
Heel slippage, focal pressure or increased discomfort with a new device should prompt review. Rather than stacking pads or repeatedly changing height independently, follow the agreed plan. Follow-up should consider function and symptoms, not only whether the person looks more level when standing. For breaking in and care, see our guide on how to use insoles.
For a child who is still growing, today's measurement does not describe the whole future picture. Follow-up and any treatment should be guided by a paediatric orthopaedic assessment. Not every child needs an immediate insole or operation; observation may form part of the plan. More substantial differences can require consideration of other orthopaedic options.
If a new feeling of unequal leg length develops after surgery, inform the surgical team. A perceived difference should not automatically be assumed to match a measured difference. A lift used before surgery should not simply be continued on the assumption that the same arrangement remains suitable afterwards.
Note when symptoms began, which movements make them worse and how walking is affected. Previous measurements, imaging reports, surgical information and existing supports can be useful. Ask which side is being supported, why the support is proposed, what its intended goal is and when it should be reviewed.
Arrange medical assessment for a new or progressing limp, ongoing pain or a noticeable loss of function. Inability to bear weight or severe pain after an injury requires prompt attention. A useful approach begins by establishing the nature of the leg length difference; heel lifts and insoles are then considered in light of that assessment. You can arrange a discussion suited to your needs.