After an artificial hip replacement, patients sometimes notice a slight but annoying difference between the length of their legs. This difference in length can change the way a person walks. It can also make walking more difficult, requiring more effort. If one of your patient’s legs is longer than the other leg, he or she has a common problem known as leg length discrepancy.
A limb length difference may simply be a mild variation between the two sides of the body. This is not unusual in the general population. For example, one study reported that 32 percent of 600 military recruits had a 1/5 inch to a 3/5 inch difference between the lengths of their legs. This is a normal variation. Greater differences may need treatment because a significant difference can affect a patient’s well-being and quality of life.
Will your body compensate for having a leg length discrepancy?
But let’s say you do have a true leg length discrepancy—from a purely mechanical perspective, it would seem obvious that you’d be off-balance, just like a car with one wheel larger than the others. But the body is a reactive machine: it can adapt to changes in running surface, footwear, and muscle strength. What’s to say it can’t change in response to a leg length discrepancy?
Several studies have been conducted to examine the extent to which the body can effectively compensate for a leg length discrepancy.
In a 2002 review article by Burke Gurney of the University of New Mexico, data is cited that unsurprisingly show that there are some demonstrable asymmetries in walking and running gait in subjects with a true leg length discrepancy or an artificially induced one (like walking with one shoe on). But interestingly, when these leg length discrepancies are corrected with a heel lift, there does not seem to be a consistent benefit.
Gurney cites a few sets of (unfortunately unpublished) data from other researchers that appear to show that compensatory heel lifts in the shoes of runners do not seem to improve efficiency, at least as measured by oxygen consumption.
And in an older study of walking gait, impact forces actually increased after the subjects, who had leg length discrepancies ranging from about 5-20mm, were given a heel lift to correct their discrepancy. What’s more, this increase in impact forces persisted even after a three-week “break in period,” illustrating that the lifts may have been throwing the body off balance instead of stabilizing it.
There are many causes of limb length discrepancy. Some include:
Previous Injury to a Bone in the Leg
A broken leg bone may lead to a limb length discrepancy if it heals in a shortened position. This is more likely if the bone was broken in many pieces. It also is more likely if skin and muscle tissue around the bone were severely injured and exposed, as in an open fracture.
Broken bones in children sometimes grow faster for several years after healing, causing the injured bone to become longer. A break in a child’s bone through the growth center near the end of the bone may cause slower growth, resulting in a shorter leg.
Bone infections that occur in children while they are growing may cause a significant limb length discrepancy. This is especially true if the infection happens in infancy. Inflammation of joints during growth may cause unequal leg length. One example is juvenile arthritis.
Bone Diseases (Dysplasias)
Bone diseases may cause limb length discrepancy, as well. Examples are:
- Multiple hereditary exostoses
- Ollier disease
Other causes include inflammation (arthritis) and neurologic conditions
Sometimes the cause of limb length discrepancy is unknown, particularly in cases involving underdevelopment of the inner or outer side of the leg, or partial overgrowth of one side of the body. These conditions are usually present at birth, but the leg length difference may be too small to be detected. As the child grows, the limb length discrepancy increases and becomes more noticeable. In underdevelopment, one of the two bones between the knee and the ankle is abnormally short. There also may be related foot or knee problems.
Hemihypertrophy (one side too big) or hemiatrophy (one side too small) are rare limb length discrepancy conditions. In these conditions, the arm and leg on one side of the body are either longer or shorter than the arm and leg on the other side of the body. There may also be a difference between the two sides of the face. Sometimes no cause can be found. This is known as an “idiopathic” difference.
Limb length discrepancy can be measured by a physician during a physical examination and through X-rays.
Usually, the physician measures the level of the hips when the child is standing barefoot. A series of measured wooden blocks may be placed under the short leg until the hips are level. If the physician believes a more precise measurement is needed, he or she may use X-rays. In growing children, a physician may repeat the physical examination and X-rays every six months to a year to see if the limb length discrepancy has increased or remained unchanged.
A limb length discrepancy may be detected on a screening examination for curvature of the spine (scoliosis). But limb length discrepancy does not cause scoliosis.
The effects of limb length discrepancy vary from patient to patient, depending on the cause and size of the difference. Differences of 3 1/2 percent to 4 percent of the total length of the leg (about 4 cm or 1 2/3 inches in an average adult) may cause noticeable abnormalities when walking. These differences may require the patient to exert more effort to walk.
There is controversy about the effect of limb length discrepancy on back pain. Some studies show that people with a limb length discrepancy have a greater incidence of low back pain and an increased susceptibility to injuries. Other studies do not support this finding.
Physical Therapy Management
The non-surgical intervention is mainly used for the functional and environmental types of leg length discrepancies. It is also applied to the mild category of limb length inequality.
Non-surgical intervention consists of stretching the muscles of the lower extremity. This is individually different, whereby the M. Tensor Fascia latae, the adductors, the hamstring muscles, M. piriformis and M. Iliopsoas are stretched.
In this non-surgical intervention belongs also the use of shoe lifts. These shoe lifts consists of either a shoe insert (up to 10-20mm of correction), or building up the sole of the shoe on the shorter leg (up to 30-60mm of correction). This lift therapy should be implemented gradually in small increments.
Several studies have examined the treatment of low back pain patients with LLD with shoe lifts. Rehab Experts obtained good results: the patients experienced major or complete pain relief that lasted upon follow-up ranging from 3 to 11 years. We also observed patients whereby 44% experienced complete pain relief, and 45% had moderate or substantial pain relief. Our studies shows that 157 (of 211) patients with LBP, treated with shoe lifts, were symprom-free after a mean follow-up of 18 months.
LLD and Low Back pain.
Shoe lifts can reduce low back pain, if patients’ low back pain is correlated to the LLD. See Differential Diagnosis! Important is to gradually increase the corrective lift, rather than correct a fixed percentage of LLD . Shoe inserts appear to reduce (chronic) low back pain and functional disability in patients with LLDs of 10mm or less. It can be added to the treatment (low back exercises) . The importance of exercises lies in the fact that (one study suggest that:) the quadratus lumborus endurance ipsilateral to the supine short leg has significantly decreased endurance combared to people with no leg-length asymmetry . However, this is only 1 small observational study and further research about changes in muscle endurance and strength in people with LLD is needed.
The PALM (palpation Meter)
The PALM is a reliable and valid instrument for measuring pelvic height difference (PD). It is convenient, cost-effective and is a good alternative to radiographic measurement!
2 tape strips were placed on the ground, 15cm apart. The tape strips mark the location on the floor were patients have to place their feet. The patients are asked to walk for 10 steps and the align the medial borders of their feet with outside of the tape strips. Patients have to stand fully erected (no knee or hip or spine bending). The PALM is placed on the most superior aspect of the iliac crest. The distance between caliper heads are measured to the nearest mm and the angle of inclination to the nearest half degree. The inclinometer ball is designed to move towards the side of the shorter limb.