Board of Certification for the Athletic Trainer (BOC) Practice Test

What is the interpretation of a 15 mm difference in apparent leg length measurements?

1. Functional leg length difference is negative

2. Functional leg length difference is positive

3. The athlete has no significant muscle tightness

4. The right leg length measurement is longer

The correct answer is: Functional leg length difference is positive

A 15 mm difference in apparent leg length measurements indicates a positive functional leg length difference. This means that one leg appears longer than the other when measured from a specific anatomical landmark, such as the umbilicus, to the medial malleolus of each leg. An apparent leg length discrepancy can often be attributed to factors such as pelvic positioning, muscle tightness, or structural imbalances rather than an actual difference in bone length. In this case, a 15 mm difference suggests that the measurements reflect a notable functional discrepancy that may require further assessment to understand the underlying cause. The other choices do not accurately reflect the meaning of a 15 mm difference. A functional leg length difference being negative would imply that one leg appears shorter than it is, which is not the case here. The statement about the athlete having no significant muscle tightness does not specifically relate to the measurement difference, as tightness could still influence the interpretation. Lastly, without knowing which leg is longer, it cannot definitively conclude that the right leg is longer. The measurable difference itself confirms the positive aspect of the leg length discrepancy.