Leg length differences (LLD) can occur in all age groups and is not necessarily always due to odd bone lengths but commonly due to soft tissue tightness. For example, hip and knee operations may cause LLD and tightness to the lower back muscles that insert into the pelvis could cause a pelvic tilt and, hence, a LLD.
Treament involves a comprehensive musculoskeletal examination and often a single insole to go inside the shoe to raise the shorter limb.