Leg length discrepancy

Leg length discrepancy is a limb length discrepancy in which the legs are uneven as a result of bony involvement (i.e., anatomical leg length discrepancy) or muscular abnormalities (i.e., functional leg length discrepancy). Leg length discrepancy may be idiopathic, congenital, or acquired. Individuals are often asymptomatic but, if present, symptoms include a limp and hip and/or back pain. Leg length discrepancy is diagnosed based on clinical leg length measurements and confirmed with imaging studies (e.g., standing full-length hip to ankle x-ray). Management depends on the underlying cause and degree of length discrepancy. Treatment for anatomical leg length discrepancy includes watchful waiting, shoe lifts, and surgery (e.g., leg-lengthening and/or leg-shortening procedures). Complications of leg length discrepancy include functional impairment, compensatory structural and gait abnormalities, and osteoarthritis.

• Prevalence in children is unknown. ^[1]
• In adults:
  • 90% have some degree of leg length discrepancy. ^[2]
  • Up to 35% have a discrepancy of 0.5–1.5 cm. ^[1]
  • 6.4% have a discrepancy of ≥ 1.5 cm. ^[2]

Epidemiological data refers to the US, unless otherwise specified.

Anatomical leg length discrepancy ^[1][3]

• Idiopathic (most common)
• Congenital conditions
  • Hemihyperplasia
  • Skeletal dysplasias
  • Absent or shortened leg bones (e.g., fibular hemimelia)
  • Developmental dysplasia of the hip
• Acquired
  • Surgery
  • Fracture, especially if it involves an open physis (e.g., Salter-Harris type II fracture)
  • Tumor ^[4]
  • Infection
  • Inflammatory arthritis
  • Radiation

Functional leg length discrepancy ^[1][3]

Muscular abnormalities as a result of:

• Pelvic tilt from muscle imbalances (e.g., hip adduction or abduction deformities)
• Neurological conditions (e.g., cerebral palsy)
• Contractures
• Compensation for bony abnormalities elsewhere in the body (e.g., scoliosis)

Symptoms ^[1]

• Often asymptomatic
• Limp
• Hip and/or back pain

Physical examination ^[1]

Observation of standing and gait assessment may show:

• Asymmetries in the spine and/or hips (e.g., laterally tilted pelvis, lumbar curvature)
• Attempts to even the legs (e.g., bending the knee of the longer leg, tiptoe standing on the shorter leg)
• Abnormal gait

Approach ^[2]

• Perform an objective assessment of leg lengths, e.g. with: ^[2]
  • Block testing
  • Galeazzi test ^[5]
• Use direct measurement to help differentiate anatomical and functional leg length discrepancies. ^[2][6]
  • Anatomical leg length discrepancy: Measure each leg from the anterior superior iliac spine to the medial malleolus. ^[3]
  • Functional leg length discrepancy: Measure from the umbilicus to the medial malleoli of each ankle.
• Obtain imaging if the cause of the discrepancy is anatomical or unclear.
• Perform further diagnostics as appropriate to determine underlying etiology, e.g., diagnostics for scoliosis.

Imaging

In patients with suspected leg length discrepancy, imaging is indicated to confirm and quantify the discrepancy. Imaging may also identify an underlying cause. ^[1][6]

• Initial imaging ^[7]
  • Preferred: standing full-length anterior-posterior hip to ankle x-ray (teleoroentgenogram)
  • Alternative: scanogram
• Additional imaging studies
  • Bone age (in children): to help estimate the predicted leg length discrepancy when skeletal maturity is reached ^[1]
  • Ultrasound, CT, or MRI may be used to assess etiology or plan surgery. ^[2][8][9]

• Management of leg length discrepancy varies depending on the underlying cause and severity.
• Refer all children with congenital causes of leg length discrepancy to orthopedics to assess for associated joint abnormalities. ^[1]

Functional limb length discrepancy ^[3]

• Treat underlying cause.
• Offer physical therapy.

Anatomical leg length discrepancy

Management is based on degree of discrepancy (or predicted discrepancy). ^[1]

< 2 cm discrepancy ^[1][3]

• Asymptomatic patients: observation and reassurance
• Symptomatic patients (e.g., abnormal gait or pain): Refer for shoe lifts.
• Worsening discrepancy or symptoms: Refer to orthopedics.
• Children: Repeat imaging may be indicated to monitor for progression until skeletal maturity. ^[8]

≥ 2 cm discrepancy ^[1][3]

• Refer to orthopedics for surgical evaluation.
• Options include:
  • Leg shortening of the longer leg, e.g., with:
    • Epiphysiodesis: surgical fusion of the growth plate (if not skeletally mature)
    • Acute shortening: e.g., with bone resection (if skeletally mature)
  • Leg lengthening of the shorter leg, e.g., with distraction osteogenesis
  • Use of external prosthesis if discrepancy is > 20 cm ^[1]

• Functional impairment
• Compensatory structural and gait abnormalities (e.g., functional scoliosis or limp)
• Degenerative joint processes (e.g., osteoarthritis of the hip or knee)

We list the most important complications. The selection is not exhaustive.