Limb length discrepancy, also known as limb length inequality or anisomelia, is a condition in which an individual’s arms or legs are of unequal lengths. Many people have an arm or a leg that is shorter or longer than the other, but the discrepancy is often small enough that it does not cause any problems. It is estimated that up to 35% of adults have a 0.5-to-1.5-centimeter limb length discrepancy.

Though less common, larger discrepancies in limb length can interfere with day-to-day activities. For instance, a person with an arm length discrepancy—that is, with arms of unequal lengths—may have difficulty performing certain activities, including those that require both hands to be the same distance from the body, such as steering a bicycle. Leg length discrepancies—when the legs are of unequal lengths—can cause limping and an abnormal gait. It can also cause problems with posture and lead to hip and back pain.

Fortunately, various treatments are available including orthotics such as shoe lifts, assistive devices, and surgery to shorten or lengthen limbs. “It’s very common for people to have small differences in length that they never notice,” says David Frumberg, MD, a Yale Medicine specialist in treating orthopaedic conditions that include limb length differences. “Treatment can be considered if the difference becomes significant enough.”

A limb length discrepancy is when one arm or leg is shorter or longer than the other arm or leg; it may affect an entire limb or only part of it. Sometimes, the discrepancy occurs due to a disorder or disease that affects the growth of an arm or a leg during early development, when the fetus is in the womb. In such cases, the limb length discrepancy is present at birth. However, limb length discrepancies may also be acquired, meaning they develop after birth due to a number of possible causes, including bone infections, certain types of arthritis, or bone fractures that do not heal properly.

Limb length discrepancy may be congenital (present at birth) or acquired (acquired after birth).

Causes of congenital limb discrepancy include:

• Developmental dysplasia of the hip (when the acetabulum, or “socket” of the hip joint, does not develop correctly)
• Hemiatrophy (when one side—or part of one side—of the body, such as an arm or a leg, does not grow properly and is thereby shorter than the other side)
• Hemihypertrophy (when one side—or part of one side—of the body, such as an arm or a leg, grows more than the other side and is thereby larger and longer)
• Overgrowth syndromes (conditions characterized by excessive growth), including:
  • Beckwith-Wiedemann syndrome
  • Klippell-Trenaunay syndrome
  • Proteus syndrome
• Femoral, fibular, tibial, radial, ulnar, or humeral deficiency (when one of the bones in the leg—the femur, fibula, or tibia—or in the arm—radius, ulna, or humerus—is short or absent)

Causes of acquired limb length discrepancy include:

• Physical trauma to the affected bone, including:
  • Bone fracture that heals in a way that results in a shortened limb
  • Growth plate fracture, or physeal fracture (a fracture of the growth plate may cause the affected bone to grow faster or slower than normal)
  • Burns
  • Surgery, such as a failed joint replacement procedure
  • Radiation therapy received before reaching skeletal maturity (that is, while the bones are still growing)
• Infections, including:
  • Osteomyelitis (bone infection)
  • Septic arthritis (joint infection)
  • Tuberculosis
• Some types of arthritis, including:
  • Rheumatoid arthritis
  • Juvenile idiopathic arthritis
• Some neuromuscular diseases, including:
  • Cerebral palsy
  • Polio
• Neurofibromatosis type 1 (a disease in which tumors develop in the central nervous system and which can lead to bone deformities)
• Ollier disease (a disorder in which benign, or noncancerous, growths of cartilage form in the bones that can disrupt normal bone growth)
• Hereditary multiple osteochondromas (also known as hereditary multiple exostoses, this condition is marked by the growth of benign bone tumors that can reduce bone growth)

In many cases, the exact cause of limb length discrepancy is unknown.

The symptoms of limb length discrepancy may vary based on the size of the discrepancy, which limb is affected, and its cause. In general, smaller differences in length between the limbs result in fewer, more mild symptoms.

Symptoms of leg length discrepancy may include:

• Limp
• Walking on balls of feet or toes of the shorter leg to compensate for the length discrepancy
• Hip pain
• Back pain
• Scoliosis (a sideways curve of the spine)
  

Symptoms of arm length discrepancy may include:

• Difficulty performing some tasks in which the arms and hands are at an equal distance from the body and/or must work with coordinated movement such as typing on a keyboard, playing the piano, carrying objects, or playing certain sports

Limb length discrepancies may also affect a person’s body image and self-esteem.

Parents and/or patients are often the first to recognize a limb length discrepancy. For example, they may notice a limp or other gait abnormality. Sometimes, leg length discrepancies are identified during school screenings for scoliosis. Congenital limb length discrepancies are often observed and diagnosed shortly after birth.

To diagnose or confirm a limb length discrepancy, doctors may review the patient’s medical history, conduct a physical exam, and order one or more diagnostic tests.

The doctor will ask about the patient’s symptoms and potential causes of a limb length discrepancy, such as whether they have a history of an injury, burn, or infection of the affected limb. They may also ask if the patient has a family history of skeletal dysplasia, a group of inherited disorders that affect bone growth and development.

During the physical exam, the doctor will examine the limbs to assess whether they are of unequal length. The doctor will assess the range of motion of the joints in the limb to check for potential causes of length discrepancy. They will watch the patient walk to determine whether there are any gait abnormalities indicative of a leg length discrepancy. The doctor may also examine the patient’s spine for signs of scoliosis or other abnormal spinal curvatures.

To determine whether the legs are of unequal length, the doctor will place blocks of different heights under the foot of the suspected short leg until the pelvis is level. By measuring the height of the block, the doctor can assess the length discrepancy. The doctor may also use a tape measure to measure the length of each leg.

Imaging tests are also used to diagnose and assess the degree of limb length discrepancy. These tests may include:

• X-ray imaging allows doctors to visually examine the bones to determine whether there is a length discrepancy and identify bone abnormalities that may cause or contribute to the discrepancy. A ruler may be placed next to the limb during the X-ray to help doctors measure the size of the length discrepancy.
  
  Different types of X-ray imaging may be used, including scanograms and orthoroentgenograms. Both tests involve taking three X-rays, one of the hips, another of the knees, and another of the ankles. A ruler is included in the X-rays, allowing doctors to assess the length of the legs.
• Computed tomography (CT) scans use X-rays to produce images of cross-sections of internal body structures.
• EOS imaging uses low-dose X-rays to produce full-body images of the bones from the front and side. It can be used to measure limb length discrepancy. EOS imaging is available only in some medical centers and hospitals.

For children who are still growing, doctors may also order an X-ray of the hand and wrist to establish bone age. Bone age, a measure of the maturity of the bone, can differ from a child’s chronological age. Determining a child’s bone age helps doctors estimate how much more the child may grow, as well as the degree of the limb length discrepancy when they stop growing. Bone age is an important factor in determining the best treatment options.

Doctors may also order additional tests to determine whether the patient has a medical condition that could cause or contribute to limb length discrepancy.

For people with mild limb length differences, there is generally no effect on health or activities. If limb length differences are untreated, back and hip problems may develop. After limb length equalization, whether by orthotic or surgery, the secondary effects of limb length differences are alleviated.

“Patients will get innovative care with the most advanced techniques at Yale Medicine,” Dr. Frumberg says. “An entire team of specialists is needed for successful limb lengthening surgeries. This includes physical therapists, nurses, and pain management experts. We also have world-class specialists in physiatry, psychology, and bone endocrinology, all of whom work diligently to ensure someone opting for limb lengthening surgery has the best result.”