Understanding Limb Length Discrepancy (LLD)

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Limb Length Discrepancy (LLD) is a condition where one arm or leg is shorter than the other. While minor differences are common and often go unnoticed, a significant discrepancy can affect a person’s gait, posture, and long-term joint health. The causes of LLD are diverse, ranging from issues present at birth to injuries sustained later in life.
1. Congenital Causes (Present at Birth)

Some children are born with conditions that affect the growth of bones in the legs or arms. In these cases, the discrepancy is usually noticed in early childhood.

• Congenital Femoral Deficiency: A rare condition where the thigh bone (femur) is abnormally short or underdeveloped.
• Hemihypertrophy: A condition where one side of the body grows faster or larger than the other.
• Fibular Hemimelia: The partial or total absence of the fibula (the outer thin bone of the lower leg), which severely limits the growth of that limb.

2. Post-Traumatic Causes (Injuries)

Injury is one of the most common causes of unequal limb length. If a bone breaks, how it heals determines whether a discrepancy will occur.

• Growth Plate Injuries: In children, bones grow from soft areas of cartilage near the ends of long bones called epiphyseal plates.8 If a fracture occurs through this plate, the bone may stop growing prematurely or grow at a slower rate than the unaffected side.
• Malunion: This occurs when a broken bone heals in an overlapped or “shortened” position.
• Severe Comminuted Fractures: If a bone is shattered into many pieces, some bone mass may be lost during the injury or surgical cleanup, resulting in a shorter limb.

3. Infections and Diseases
Certain medical conditions can destroy growth cells or cause inflammation that alters bone development.
Osteomyelitis: An infection in the bone can damage the growth plate in a growing child, leading to stunted growth in that specific limb.
Septic Arthritis: Infection within a joint (like the hip or knee) can lead to bone loss or growth arrest.
Bone Tumors: Both benign and malignant tumors, as well as the radiation treatments used to treat them, can interfere with normal bone growth patterns.
4. Neuromuscular Conditions
Disorders that affect the nerves and muscles can lead to secondary bone growth issues. When muscles are weak or paralyzed, they do not pull on the bones with the same force, which is necessary for healthy bone stimulation and growth.
Polio: Historically a major cause, polio results in muscle weakness that often stunts the growth of the affected limb.
Cerebral Palsy: Muscle spasticity or weakness can lead to hip dislocations or structural changes that make one leg appear or function as though it is shorter.
5. Idiopathic Causes
In some instances, the cause is “idiopathic,” meaning doctors cannot identify a specific injury or disease that triggered the difference. The discrepancy simply appears during the natural growth process and is monitored by specialists to ensure it does not cause orthopedic issues later in life.
6. Post Surgery
Post hip or knee replacement surgery.
Structural vs. Functional Discrepancy
It is important to distinguish between two types of unequal limb length:
Structural: The actual bone (femur or tibia) is physically shorter.
Functional: The legs are the same length, but a problem like scoliosis (curvature of the spine) or a hip contracture makes one leg appear shorter.
Teri Green
About Atlas Biomechanics: We manufacture heel lifts in the USA. Considered best heel lifts to treat limb length discrepancy.