Limb Length Discrepancy (LLD) & back pain

Limb Length Discrepancy (LLD) means one limb is shorter than the other, most commonly the legs. A small difference is extremely common and usually harmless, but larger discrepancies can cause back pain, affect gait, posture, long‑term joint health.
Most people have minor differences (<1 cm) that cause no issues.
Differences >2 cm are more likely to cause symptoms and may require evaluation.
It is divided in two group:

• Structural — an actual difference in bone length.

• Functional — bones are equal, but posture, joint contracture, or muscle imbalance makes one limb act shorter. 

Why It Happens

LLD can be congenital (present at birth) or acquired. Common causes include:

• Growth plate injuries

• Fractures that heal short or overgrow

• Bone infections (osteomyelitis)

• Bone diseases such as neurofibromatosis or multiple hereditary exostoses

• Hip disorders (e.g., developmental dysplasia)

• Neuromuscular conditions (e.g., cerebral palsy)
   

How LLD Is Diagnosed

Diagnosis typically includes:

• Physical exam and gait analysis

• Block testing (placing blocks under the short leg until the pelvis levels)

• Imaging: Full length X‑rays, scanogram, or CT for precise measurement
   

Symptoms You Might Notice

Symptoms depend on the size of the discrepancy:

• Limping or toe-walking

• Lower and upper back pain

• Uneven hips or shoulders

• Back, hip, knee, or ankle pain

• Fatigue when walking

• Functional scoliosis (spine curves to compensate)

• heel cracks 
  
  

Treatment Options

Treatment depends on severity, age, and cause.

heel lift (for <2 cm differences) 

• Observation during growth

• Physical therapy (strengthening weak muscles)
   

Surgical (for larger or symptomatic discrepancies)

1. Epiphysiodesis
   
   

   • Slows or stops growth in the longer leg

   • Used in growing children
     
     

2. Leg shortening
   
   

   • Removes or arrests growth in the longer limb

   • Suitable for moderate discrepancies
      

3. Limb lengthening
   
   

   • Gradually lengthens the shorter limb using external fixators or internal devices (e.g., PRECICE nail)

   • Used for significant discrepancies