Turf toe, or sprain of the first metatarsophalangeal (1MTP) joint, is a devastating injury to football players and accounts for a large amount of lost playing time. It is estimated that 45% of professional players sustain 1MTP sprain throughout their career (Rodeo et al. 1993). Despite the prevalence and severity of the injury, current research has neither examined the mechanisms of injury nor described the tolerance of the joint. The goal of this thesis is to identify an injury mechanism and to quantify the tolerance of 1MTP joint to sprain in an in vitro cadaveric model.

To this end, cadaveric limbs were tested to varying degrees of hyperextension while recording kinematic and kinetic parameters. Specimens were examined for injury post-test by medical professionals. Binary logistic regression was performed to assess the discriminating properties of recorded parameters, and a survival analysis was performed on the most useful parameters to assess risk of injury. Injury risk was compared to previously obtained athlete performance data to evaluate performance-injury risk tradeoff.

Twenty lower limbs (right and left) were tested. Injury was identified in 11 of these specimens. Both maximum hyperextension angle and maximum moment through the 1MTP joint were found to predict injury (γ_{max. angle, hallux,}=0.61, γ_{max. moment} =0.61). Because it is non-dimensional, hyperextension angle was identified as the most valuable discriminating parameter. The 50% risk of 1MTP sprain was found to occur at 86° of extension.

Athletic performance data collected from professional football players were used to develop a cumulative probability function for the maximum 1MTP joint angle found during several tasks. This function was found to be offset from the injury risk function. For example, 50% of peak extension angles attained during running are below 52°, which is 34° less than the angle corresponding to 50% risk of injury. This offset between the performance distribution and the injury risk function is considered to be a design space within which athletic shoes may be designed to reduce injury risk without compromising athletic performance.