Leg Length Discrepancy, aka Short Leg Syndrome, and Heel Lifts

A number of causes can contribute to leg length discrepancy, including:

• Any bone in the leg ever broken, particularly during growth years,
• Congenital differences or uneven growth,
• Disease-caused shortening of the muscles and connective tissue, a common after-effect of polio,
• Surgically-induced differences, especially common after hip replacement surgery,
• Compensation for problems elsewhere in the body, such as pelvic or spinal scoliosis.

These biomechanical adaptations and compensations for even a slightly short leg can have long-term side-effects, manifesting as lower back pain, hip and knee pain, uneven gait, and various foot and lower leg problems. These problems are often related to the bodily adaptations that occur due to continuing unbalanced movement, and can be aggravated by the extra stresses of sports activities  such as running.

The diagnosis and treatment of such leg length differences and their effects is the subject of volumes of medical history and research, and is not the subject of this document. The use of heel lifts should generally be prescribed after thorough medical evaluation. 

The intent of these recommendations is simply to assist you in choosing among the wide variety of in-shoe heel elevating products, and in recommending how to use them for your personal needs.

Short leg syndrome or anatomical (structural) or functional (adaptive) leg length discrepancy, is often treated using heel lifts or shoe lifts.

Heel lifts, also known as shoe lifts, are firm wedge-shaped inserts for shoes, which attempt to better balance the lower body by adding to the length of the short leg at the point when the heel strikes the ground while walking.

Treating Leg Length Discrepancy Using Heel Lifts

• Heel lifts for leg length compensation will only be required for the short leg, i.e. in one shoe. This can make the two shoes fit and feel different, particularly if the heel lift adds cushioning in the shoe. You will be most comfortable if no additional cushioning is added by the heel lift.
• Because leg length compensation will typically be needed permanently, long-term comfort and minimum stress on the foot is very important - see Selecting Heel Lifts and Shoe Lifts - A Guide for more information on choosing heel lift products.
• As much as possible, the same elevation should be added in all shoes that are regularly worn, including house-slippers and flip-flops. You will probably need more than one type of heel lift or modification for various footwear.
• It is generally accepted that no more than 12mm (1/2") of heel elevation can be used in a shoe without affecting stability. The maximum height you can use in a pair of shoes will be affected by the style and fit of the shoes, as well as your foot size. Laced shoes will permit more heel lift height, for example.
• If you require more than 10-12mm of compensation, part of the additional height should be added to the external sole and heel, rather than inside the shoe. This will cause less stress on the foot and lower leg. More than 12mm should be added as a full-foot lift, either inside or outside the shoe, or both, rather than just a heel lift.
• When introducing your body to the use of heel lifts, increase to the target height slowly - add 2-3mm each week on the short leg side, to allow the body to adapt to the change. Adjustable shoe lifts are useful for this purpose.
• The ideal height for your specific needs should be determined by experimentation over a long time. You may find that a difference of 1-2mm greatly improves your overall comfort both in the shoe, and in the other effects of your leg length discrepancy. Try changing the shoe lift height slightly and evaluating the effects for a few days or weeks.
• It is often recommended that the starting point for heel lift height be one-half of the measured difference in leg length. It is my personal belief that this should be modified based on the length of time that the difference in leg lengths has existed:
  - In the case of an uncompensated leg length difference that has existed for a long time, the body will have adapted to the imbalance, and completely compensating for the leg length difference may make these changes maladaptive - you may cause new problems by using a heel lift of the full height of the measured difference, at least initially.
  - For recent changes, such as surgically-induced leg length differences, or in children, where bone growth is still occurring, I believe that the heel lift height should fully compensate for the difference, to minimize adaptive changes if possible.
• Use of heel lifts is a medical and personal decision, but it is strongly recommended that a health care professional be involved in the evaluation of the need and in monitoring the results.