Leg Length Discrepancy

Overview

Leg length discrepancy means that one leg is shorter than the other. Small differences are extremely common and usually cause no problems. Larger differences can affect the way a person stands and walks and may, over time, contribute to discomfort in the hip, knee, or back.

There are two main types. A structural (true) discrepancy means the bones of one leg are actually shorter. A functional (apparent) discrepancy means the bones are the same length, but the leg appears or behaves as if shorter because of issues such as muscle tightness, joint contractures, or pelvic tilt. Identifying which type is present guides treatment.

Symptoms

Many small discrepancies cause no noticeable symptoms. When a difference is large enough to matter, signs may include:

• A visible limp or uneven walking pattern.
• The feeling that one leg is shorter or that the body tilts to one side.
• Hip, knee, or low back pain, often worse with standing or walking.
• Walking on the toes of the shorter leg, or bending the knee of the longer leg.
• Uneven shoulders or pelvis when standing.
• In children, an obviously uneven gait noticed by parents.

Symptoms tend to appear when the difference is more pronounced or when the body has worked to compensate for it for a long time.

Causes

Leg length discrepancy can be present from birth or develop later. Causes include:

• Differences in bone growth, sometimes from injury to a growth plate in childhood.
• Fractures that heal with the bone slightly shortened, or that affect growth in children.
• Bone infections or tumors affecting one limb.
• Conditions present at birth, such as developmental problems of the hip or underdevelopment of bones in one leg.
• Joint conditions such as arthritis or hip disorders.
• Functional causes such as muscle tightness, scoliosis, pelvic tilt, or joint contractures, in which the bones are actually equal in length.

Risk Factors

Factors that can increase the likelihood of a meaningful leg length difference include:

• A childhood fracture involving a growth plate.
• Bone or joint infections during the growing years.
• Certain conditions present at birth affecting the hip or leg bones.
• Hip conditions such as hip dysplasia.
• Scoliosis or significant muscle imbalance, which can cause a functional discrepancy.
• Previous major surgery on the hip, knee, or leg.

Diagnosis

Diagnosis combines examination with measurements and imaging to determine the size and type of the discrepancy. It may include:

• Physical examination, watching the person walk and stand, and checking posture and the pelvis.
• Tape-measure assessment of leg length and use of blocks under the shorter leg to see how much height levels the pelvis.
• X-rays to measure bone lengths precisely.
• Specialized imaging such as a scanogram or CT in some cases for accurate measurement.
• In growing children, imaging may be repeated over time to estimate how the difference will change.

Treatment

Treatment depends on the size of the difference, whether it is structural or functional, the person's age, and whether it causes symptoms. Options include:

• No treatment for small differences that cause no problems.
• Shoe lifts or inserts to even out the legs, the most common treatment for mild to moderate discrepancies.
• Physical therapy to stretch and strengthen muscles, especially for functional discrepancies.
• Surgery for larger differences, which may involve slowing growth in the longer leg of a growing child, shortening the longer leg, or lengthening the shorter leg.

For functional discrepancies, treating the underlying cause, such as muscle tightness or pelvic tilt, may resolve the apparent difference without a lift or surgery.

Prevention

Many causes cannot be prevented, but some steps may reduce risk or limit the effect:

• Seeking prompt treatment for childhood fractures, especially those near growth plates.
• Treating bone and joint infections early.
• Addressing muscle imbalances, tightness, and posture problems that can lead to a functional discrepancy.
• Regular checkups for children with known hip or limb conditions so changes can be tracked.

When to See a Doctor

See a doctor if you or your child has a noticeable limp, uneven legs, or hip, knee, or back pain that may be related to leg length. A growing child with a visible discrepancy should be evaluated promptly, since timely treatment can influence final leg lengths.

Seek prompt care if a leg length difference develops suddenly after an injury or comes with significant pain, swelling, or inability to bear weight, as these may indicate a fracture or other problem needing urgent attention.

Related Topics

Frequently Asked Questions

References

1. American Academy of Orthopaedic Surgeons (AAOS).
2. Mayo Clinic.
3. MedlinePlus, U.S. National Library of Medicine.