re when we treat leg length discrepancies

axcerpted from the Review

Anatomic and functional leg-length inequality: A review and recommendation for clinical decision-making. Part II, the functional or unloaded leg-length asymmetry
by Gary A Knutson *

Conclusion
Anatomic leg-length inequality under 20 mm and leg¬length alignment asymmetry caused by supra-pelvic mus¬cle hypertonicity may interact in a loaded (standing) pos¬ture, but not in an unloaded (prone/supine) posture. Any leg-length alignment asymmetry due to suprapelvic mus-cular hypertonicity should be eliminated before any nec-essary treatment of anatomic leg-length inequality. By using this information, which is open to change based on new studies, the clinician may better understand the diverse and sometimes confusing findings relative to ana¬tomic leg-length inequality and functional or unloaded leg-length alignment asymmetry, and be better able to make treatment recommendations.