What is a leg length discrepancy?
Leg length discrepancies can vary anywhere from 4mm to 60mm. The greater the discrepancy, the more a person must compensate his or her normal posture and gait (walking pattern) in day to day life. The body has a righting reflex, meaning that it will attempt to compensate for any postural imbalance. The degree of compensation probably depends on whereabouts in the body it occurs. This can lead to a variety of symptoms, such as functional scoliosis, hip, knee and ankle problems.
Long term imbalances will not only contribute to chronic pain, but lead to problems causing postural changes in the body from the back down to the foot. Walking with a short leg increases energy use, places increased stress on the longer leg and can cause a compensatory functional scoliosis. The foot is also a great compensator and will alter its functional position to even up the leg length. This is a contributor to foot pathology.
Small, seemingly inconsequential leg length differences (LLD) are often considered irrelevant. Our experience has yielded a different result. Minimal leg length discrepancy can contribute to significant symptoms of gait abnormalities and pain.
Leg length discrepancies occur in a large percent of the population. Although they do not always lead to problems, any discrepancy needs to be taken into consideration when undergoing podiatric assessment for postural anomaly and foot pathology. Interestingly a leg length discrepancy is a common cause of running injuries.
There are generally two kinds of leg length discrepancies:
Structural (actual) discrepancy occurs when:
- Either the upper (femur) or lower (tibia) bone in one leg is actually shorter than that of the other leg.
- Structural discrepancies can result from a growth plate injury during childhood or adolescence, fractures or genetic and acquired conditions that affect bone growth. Some fractures can lead to overgrowth of bone during the healing process, resulting in longer than normal bone.
- Surgical procedures such as knee or hip replacement can result in a leg length discrepancy.
Functional (apparent) discrepancy usually occurs as a result of:
- Muscular weakness or inflexibility, at the pelvis or foot and ankle.
- Over a number of years, one side of the spine, and muscle structure supporting it, may develop more strongly than the other. Overuse of one side such as sleeping or carrying items on one side; or lifting suitcases or carrying children to one side
- Acquiring injuries when as a child or even forceps delivery at birth can result in a functional imbalance.
- It may be the result of a scoliosis and pelvic tilt.
Common signs and Symptoms of Leg Length Discrepancy
The symptoms of a leg length discrepancy vary widely and are more likely to relate to the underlying cause and the biomechanical imbalance resulting from it. The spine, pelvis and lower extremity may all be involved in the compensation of leg length discrepancy.
A Leg Length Discrepancy will cause the center of gravity to move to the short leg side. Common compensations include: a pelvic tilt to the short side, lumbar scoliosis (convex to the short side), increased knee flexion on the long side), an overextended knee on the short side, increased subtalar joint pronation on the long side, and ankle plantar flexion and foot supination on the short side.
Some signs include:
- Iliotibial band syndrome (pain on the outside or lateral part of the knee).
- Piriformis syndrome (buttock pain, not to be confused with sciatica, where the pain runs down the back of the leg).
- Low back pain.
- One leg is obviously shorter than the other (although this is not always obvious, due to upper body compensations such as functional scoliosis.
- Gait problems, such as limping, toe-walking, or rotation of the leg. A knee that's chronically hyper extended on the short side and flexed on the long side.
- Pain in the back hip, knee, and/or ankle.
- Symptoms affecting the lower limb that has a structural discrepancy usually appear first on the long leg side and include buttock pain, arthritis of the knee or hip, psoasitis, patellar tendonitis, patellofemoral pain syndrome, plantar fasciitis, medial tibial stress syndrome or metatarsalgia. Symptoms of the short leg include iliotibial band syndrome with lateral knee pain, trochanteric bursitis, sacroiliac discomfort, Achilles tendinitis and cuboid syndrome.
- If the patient just has a functional Leg Length Discrepancy, the symptoms will usually appear on the short side first and include plantar fasciitis, medial tibial stress syndrome, patellofemoral pain syndrome, illiotibial band syndrome, ipsilateral sacroiliac discomfort with contralateral low back pain, and secondary psoasitis
There are several ways to detect LLD.
- The simplest way is through observation and palpation.
- A complete medical history of the patient and a physical examination is required.
- Leg measurement using a tape measure may be taken.
- Biomechanical assessment will determine a functional or structural discrepancy and the presence of any compensations.
- X-rays can be used to obtain an accurate measurement of leg length discrepancy and spinal compensation.
- A CT or CAT scan (Computerized tomography scan) will scan both soft tissue and bone and may give a more comprehensive picture than X-ray.
- An analysis of day to day activity and incidence of symptoms will help determine the level of intervention required.
The treatment for LLD will depend on:
- Whether or not symptoms are present. The body may be compensating for a leg length discrepancy without causing any biomechanical stress in other areas. Therefore correcting the discrepancy may not be advisable, and in fact may lead to injury. If the discrepancy is causing symptoms, intervention is required.
- Treatment also depends on the classification of the discrepancy. A Structural leg length discrepancy will probably require the use of a heel or foot lift. Treating a functional leg length discrepancy is a little less straight forward. If a functional leg length discrepancy is found and the discrepancy is reducible, a stabilising functional orthotic and muscle stretching/strengthening programme may be effective. Any treatment should be done as part of a whole approach to reducing all symptoms, not just a short leg.
- Address the problem of heel wear on shoes. Worn heels can lead to an increase in instability and lead to possible injuries.