A set of risk equations was derived to estimate the probability of sustaining a moderate-to-serious injury to the knee-thigh-hip complex (KTH) in a frontal crash. The study consisted of four parts. First, data pertaining to knee-loaded, wholebody, post-mortem human subjects (PMHS) were collected from the literature, and the attendant response data (e.g., axial compressive load applied to the knee) were normalized to those of a mid-sized male. Second, numerous statistical analyses and mathematical constructs were used to derive the set of risk equations for adults of various ages and genders. Third, field data from the National Automotive Sampling System (NASS) were analyzed for subsequent comparison purposes. Fourth, the fidelity of the resulting set of risk equations was assessed by using the risk equations to transform the axial compressive femur loads from simulated, full-engagement, frontal crashes into event risks, and the resulting model-based injury rates were compared with the field-based injury rates. The results were promising:​ For unbelted drivers in towaway frontal crashes involving 1985-1997 model year passenger cars whose speed changes were less that 58 km/h, the model-based average injury rate was 1.10%;​ the field-based rate was 1.30%. Moreover, some of the trends in the field were confirmed with the model (e.g., there were more KTH-injured males than KTH-injured females). The risk equations demonstrated better fidelity for lower-speed crashes than high-speed crashes.