If the right ASIS appears lower than the left ASIS on an anterior view, which leg length discrepancy is most plausible?

If the right ASIS appears lower than the left ASIS on an anterior view, which leg length discrepancy is most plausible?

• A. Short right lower extremity
• B. Short left lower extremity
• C. Equal leg lengths
• D. Long right lower extremity

Answer: (A)

When you look at someone from the front, the ASIS landmarks sit on the pelvis to show how the pelvis is tilting. If one leg is shorter, the pelvis drops on that side to keep the spine upright, so the ASIS on the short-leg side appears lower than the other side. So, a right ASIS that sits lower than the left indicates the right leg is shorter. If the right leg were longer, the right ASIS would be higher; if both legs were equal, the ASIS would be level. A short left leg would instead drop the left ASIS. Therefore, the most plausible leg length discrepancy is a shorter right lower extremity.

When you look at someone from the front, the ASIS landmarks sit on the pelvis to show how the pelvis is tilting. If one leg is shorter, the pelvis drops on that side to keep the spine upright, so the ASIS on the short-leg side appears lower than the other side. So, a right ASIS that sits lower than the left indicates the right leg is shorter. If the right leg were longer, the right ASIS would be higher; if both legs were equal, the ASIS would be level. A short left leg would instead drop the left ASIS. Therefore, the most plausible leg length discrepancy is a shorter right lower extremity.