Causes. Leg length discrepancies can be caused by poor alignment of the pelvis or simply because one leg is structurally longer than the other. Regardless of the reason, your body wants to be symmetrical and will do its best to compensate for the length difference.
Date of Onset. When the Social Security Administration (SSA) refers to a disability applicant's Date of Onset, they are referring to the date that a Social Security Disability applicant became disabled. When you fill out your Social Security Disability claim forms, you will be asked to provide the date your disability began.
The disability starting point is called the onset date. Sometimes, such as with this question, the actual starting point of a disability is not immediately obvious. People might continue working despite being very ill.