Leg length inequality can be due to an anatomical short leg---one leg literally shorter due to an anomaly or after a (healed) fracture in the leg---or due to a functional short leg.
A functional short leg means one leg is shorter due to disturbances or aberrance in one’s frame (bones & joints). This could be a distorted, tilted pelvis, misalignments in the spine, etc. The sum total of the imbalances & disequilibrium in the frame results in one leg shorter than the other.
I commonly see a functional short leg in my practice; it is obvious as soon as the patient is on the adjusting table. After full-body balancing via Activator Chiropractic, the patient’s legs are even again.