Leg Length Measurement (True vs Apparent) Special Test
Orthopedic Physical Examination & Clinical Assessment Guide
What is it used for?
- Differentiating True (Structural) from Apparent (Functional) Leg Length Discrepancy (LLD).
How to Perform
- True LLD: Measure from ASIS to Medial Malleolus (fixed bony points).
- Apparent LLD: Measure from Umbilicus (belly button) to Medial Malleolus (affected by pelvic tilt).
Interpretation of Results
- Positive: A difference of >1-1.5 cm is considered clinically significant.
Clinical Context & Limitations
The Leg Length Measurement (True vs Apparent) should be considered as one component of a comprehensive musculoskeletal assessment. No single special test has perfect diagnostic accuracy; thus, clinical decision-making should integrate test results with patient-reported symptoms, mechanism of injury, functional impairment, and relevant imaging.
Clinicians should be aware of potential false-positive results in patients with pain sensitisation, muscle guarding, or poor relaxation. For the Hip region, combining the Leg Length Measurement (True vs Apparent) with complementary examination tests significantly improves overall diagnostic confidence.
References
- Magee, D. J. (2021). Orthopedic Physical Assessment.
