What is a leg length discrepancy?
A limb length discrepancy is a common condition with either a structural (true bony length difference) or a functional deformity. A functional deformity can be from abnormal or altered mechanics of the hip. knee, ankle, or foot. (Khamis et al., 2018). This can result in the appearance of a quite correctable limb length discrepancy.
A limb length discrepancy has been associated with several conditions, such as foot pathologies, stress fractures and running injuries, low back pain and osteoarthritis of the hip and knee joints. (Khamis et al., 2018). While some of these can result directly in structural deformities, others could be attributed to movement pattern changes associated with prolonged injury.
What is an acceptable leg length discrepancy?
90% of the population has some anatomic leg-length inequality; the average was found to be 5.2mm (Knutson, 2005). It should be noted still that a limb length discrepancy, as small as 5mm, causes biomechanical changes in the lower limbs during gait (Khamis et al., 2018). This does not equal to symptoms or discomfort but it may be a contributing factor.
How to measure leg length discrepancy?
Gold standard is X-ray or EOS. EOS is a newer method of medical imaging system whose aim is to provide frontal and lateral radiography images, while limiting the X-ray dose absorbed by the patient.
Otherwise, a more cost-effective and simple way is where a clinician may take two tape measurements of the distance between the front of this hip (ASIS) and ankle (medial malleolus) which also has acceptable validity and reliability.
What is the treatment of a leg length discrepancy?
In structural or bony deformities that are causing symptoms there may be benefit of progressive shoe lift to help reduce these symptoms.
In the functional deformities, the management focuses on stretching and strengthening of the lower limb based on the individual’s presentation and imbalances which is unique to each patient.