Limb-Length Discrepancy

What is a limb-length discrepancy?

A limb-length discrepancy is when one leg or arm is shorter than the other leg or arm. The difference in length can range from a fraction of an inch to several inches. Some children are born with congenital limb differences that cause their legs or arms to grow at different rates. Other limb-length discrepancies are caused by serious fractures, a fracture that does not heal properly, a bone infection such as osteomyelitis, or bone tumors or bone cysts.

Compared to differing arm lengths, leg-length discrepancies are more likely to affect a child’s daily activities. Legs of two different lengths require children to change their normal posture and walking patterns. Depending on the degree of difference, leg-length disparities can lead to a variety of problems, such as functional scoliosis, and hip, knee, and ankle problems.

Children with mild arm-length discrepancies often adapt well to the difference. However, a difference in arm length of two to three inches or more can interfere with activities of daily life and should be addressed.

Types of limb-length discrepancies

  • Structural discrepancy – a bone in one leg or arm is shorter than the same bone in the other limb.
  • Functional discrepancy – bone lengths are equal in both legs or arms, but a joint contracture (low joint mobility) in a knee, hip, shoulder, elbow, or other joint throws off the symmetry in the limbs.

What are the symptoms of a limb-length discrepancy?

The symptoms of a limb-length discrepancy vary widely from child to child based on whether a leg or arm is affected, the degree of difference in length, and the cause of the condition.

Some common symptoms include:

  • one leg or arm is shorter than the other (this is not always obvious)

Signs of leg-length discrepancy

  • problems with posture, such as a tilting shoulder
  • walking problems, such as limping or toe-walking
  • a knee that's chronically hyperextended on the short side and flexed on the long side
  • pain in the back, hip, knee, or ankle

Additional signs of arm-length discrepancy

  • difficulty reaching both handlebars on a bike
  • difficulty holding the steering wheel of a car with both hands
  • difficulty sitting in or standing up from a chair with arm rests

What causes limb-length discrepancies?

Congenital (present at birth) limb-length discrepancies develop during pregnancy. Others are caused by illness or trauma.

Congenital limb-length discrepancies

  • Some children are born with limb-length discrepancies when one or more of the long bones in a leg or arm do not develop fully during pregnancy. In most cases, there is no known cause for this.
  • Some leg-length discrepancies occur when a child is born with a problem that changes the alignment of their hips, such as coxa vara or developmental dislocation of the hip.

Injury or illness-related limb length discrepancies

  • A complex fracture or a fracture that does not heal properly can slow the growth of the affected bone. Some fractures can also lead to overgrowth of bone during the healing process. This is most common in thighbone (femur) injuries.
  • Damage to the growth plate through injury or a bone infection such as osteomyelitis can affect growth. Growth plates are soft areas at each end of the long bones in the arms and legs where bone growth takes place. When a teen or young adult reaches adult height, the growth plates harden into solid bone. If the growth plate in one limb is damaged, the other limb will continue to grow and a difference in length will develop over time.
  • Bone tumors and bone cysts can block bone growth. Depending on the location and size of the tumor or cyst, removal through surgery, radiation, or chemotherapy may cause the bone to grow more slowly or stop growing altogether.
  • Cerebral palsy and other neuromuscular problems can cause problems with a child’s alignment and overall posture, possibly leading to a limb-length discrepancy.

How we care for limb-length discrepancies

The Limb-Lengthening and Reconstruction Program at Boston Children’s Hospital provides comprehensive care for children and young adults with leg or arm differences that are present at birth or caused by injury or illness. Our team, which draws on experts from both our Lower Extremity Program and Hand and Orthopedic Upper Extremity Program, has deep expertise in both non-surgical care and limb-lengthening and reconstruction procedures.

Our clinicians have treated thousands of babies, children, and young adults with conditions that range from routine to highly complex limb differences. We also offer the benefits of the extensive services available at Boston Children’s, as well as some of the most advanced clinical and scientific research in the world.

We’ll work with you and your child to review the available options and decide the best course of treatment based on your child’s individual needs.