Previous studies have shown that lower extremity injuries account for a significant portion of the injuries sustained by passenger vehicle drivers in frontal crashes, and this pattern continues to hold for newer model year vehicles. This paper explores the potential causal factors associated with the risk of moderate or more severe lower extremity injuries in frontal crashes with a particular emphasis on the role of intrusion. A categorical analysis of the relationship between floor and toe pan intrusion showed that higher levels of intrusion were related to a larger percentage of lower leg injuries. A categorical analysis of the relationship between instrument panel and knee bolster intrusion and upper leg injuries was less clear but still demonstrated that vehicles with any intrusion had a higher percentage of upper leg injuries than vehicles with no intrusion. Logistic regression models were used to estimate the independent effect of intrusion on the probability of lower extremity injuries while controlling for crash severity (change in velocity), age, gender, body mass index, vehicle age and vehicle body type. The results indicated that for all frontal crashes the odds of experiencing a lower leg injury when floor or toe pan intrusion occurred were twice the odds of experiencing a similar injury without intrusion. In full frontal crashes and in left offset and small overlap impact crashes, the lower leg injury odds ratios for intrusion versus no intrusion increased to seven. For all frontal crashes the odds of experiencing an upper leg injury when instrument panel or knee bolster intrusion occurred were four times the odds of experiencing a similar injury without intrusion. The upper leg injury odds ratios for intrusion versus no intrusion increased to eight in full frontal crashes and to 17 in left offset and small overlap impact crashes.