Leg Length Discrepancy
Leg Length Discrepancy?
A leg length inequality in small amounts is normal in humans. Most everyone has some difference in leg length from one side to the other. An actual difference of up to about 1 cm (about the thickness of a pencil) is seen in a majority of the healthy population and does not markedly affect posture or gait. Differences up to almost 2 cm rarely concerns orthopedic physicians. Nonetheless, the body may begin compensating for such a significant asymmetry without the individual realizing it.
What Causes Leg Length Inequality?
There are several causes of leg length difference and, from a myoskeletal standpoint, these are split into two groups. Into which group a cause falls depends on whether the concern is a true discrepancy or just an asymmetry in the body.
True discrepancies are considered to be structural problems. These are normally corrected for by use special footwear, orthodics, or limb-lengthening reconstruction or other surgery.
Structural:
- Bones may have slightly more or less growth during developmental years
- Other growth plate deficiencies in pediatric patients
- Genetic predisposition
- Pediatric bone infection
- Traumatic injury
- Post-surgical results (bone-setting, joint replacement/reconstruction, cartilage removal, etc.)
- Previous fractured or broken bone
- Bow-leg or knocked knee
- Hip, knee, or ankle joint defect or degeneration
- Bone loss or degeneration
- Osteo- or rheumatoid arthritis
- Cartilage degeneration
Muscle and bone compensation may also affect leg length, but these asymmetries are functional in nature. They are usually fixable by manual therapy (structural integration, massage, chiropractic adjustment), muscle activation, retraining, and strengthening (physical therapy).
Functional:
- Pelvic shift in any of six directions (full or hemi-pelvic tilt, rotation, torsion, or combination)
- Joint capsule adhesions
- Muscle innervation/inhibition/compensation
- Muscle and deep connective tissue tension limiting range of motion
- Scoliosis
- Trunk instability
- Sacroiliac dysfunction
- Iliosacral or lumbosacral unleveling
- Muscle mass asymmetry
- Foot pronation or supination
- Other muscle or joint imbalances causing or resulting in hip or tibial torsion
According to research, approximately 2/3 of the population has a functionally short right leg. Once again, however, many theories exist as to why this is the case, but doctors have been unable to agree unilaterally on any hypothesis thus far. One interesting theory revolves around the development of the fetus during its mother’s third trimester of pregnancy.
An Example
Neurologically, during this time, the fetus is thought to develop a one-side motor control dominance and opposite-side vestibular (balance) dominance. The theory then extends in what scientists term, “cerebral lateralization”, which hypothesizes that an individual will unconciously shift their weight over the vestibular dominant side. This is done by hiking the pelvis higher on the vestibular dominant side. For 2/3 of the population, the left side of the pelvis would be higher when standing, giving the appearance of the right leg being shorter.
This, of course, is just one of several theories. In this case, leg length discrepancy is caused by a complex neurological in-grain before birth and a resulting and equally complex set of shifts in the pelvic bones during developmental years after birth to compensate.
Crossover Solutions
A few structural differences from one leg to another may be helped to some degree by manual therapy. Some forms of bone and soft tissue disease and degeneration may result in muscle innervation or inhibition in its early stages, and muscle compensations undoubtedly will in later stages. In such cases, manual therapy such as physical therapy, massage, and high velocity adjustment may help reduce pain and help slow disease and degeneration. Your doctor and/or therapist will assess and evaluate specific conditions and determine whether your particular case can be assisted by non-invasive, complementary treatment.
Functional Adaptations Run Up and Down
Where functional leg length differences are concerned, the entire body from head to toe is open to the potential for cause or effect. Problems in the feet can alter the alignment of the head or anything in between. Likewise, problems in eye-leveling and neck curvature can resonate all the way down the body to the feet. Moreover, leg length variances can cause problems elsewhere as often as other problems can cause leg length variations! In simple terms, differences in leg length can be a cause or a symptom.
Because of the complexity of functional leg length problems, many assessment techniques have been designed to narrow down the cause. Even so, no single assessment method is able to make a definitive call. Instead, a variety of orthopedic tests, functional movement screens, postural analyses, and measurements are used to eliminate compensatory strain patterns and help paint a picture of what’s really going on.
References
Erik Dalton, PhD, Short Leg Syndrome, Massage Magazine (2007)
Donatelli R. The Biomechanics of the Foot and Ankle. F A Davis Co., 2006; pp. 55-9.
Leg Length Inequality, J Manipulative Physiol Ther 1992 Nov-Dec;15(9):576-90.
True or apparent leg length discrepancy: which is a better predictor of short-term functional outcomes after total hip arthroplasty? J Geriatr Phys Ther. 2013 Oct-Dec;36(4):169-74. doi: 10.1519/JPT.0b013e318282d2f1.
Functional scoliosis caused by leg length discrepancy, Jan W. Raczkowski, Barbara Daniszewska, Krystian Zolynski
Arch Med Sci 2010; 6, 3: 393-398