Over the years, ankle kinematics has been studied during simulated sub-injury or close-to-injury situations, i.e., sudden simulated ankle spraining motion on inversion platforms (Myers et al., 2003). Since these tests did not induce real injury, they could only somewhat suggest the ankle kinematics during an ankle sprain injury. The most direct way is to investigate real injuries using biomechanical measuring techniques. However, it is obviously un-ethical to do experiments where test subjects are purposefully injured, but in rare cases accidents may occur during biomechanical testing (Barone et al, 1999; Zernicke et al, 1977). This study presented an accidental supination ankle sprain injury occurred in a laboratory under a high-speed video and plantar pressure capturing setting.
One male athlete (age = 23 years, height = 1.75m, body mass = 62.6kg) wore a pair of high-top basketball shoe and performed a series of cutting motion trials in a laboratory. The university ethics committee approved the study. The subject was instructed to run forward for six meters with maximum speed, before making a rapid left turn within the capture volume. In the fourth trial, the athlete accidentally sprained his right ankle with a supination mechanism.
The ankle motion was assessed using traditional marker-based motion analysis as well as a model-based image-matching technique for 3D reconstruction.
The analysis showed that the injury situation deviated from the non-injury trials by a sudden inversion and internal rotation after 100-120 ms. Furtermore, the injury surprisingly occurred in 10-20° dorsiflexion. This finding is in contrast to previous hypotheses where a lateral ankle sprain occur in considerable plantar flexion. These hypotheses are however based solely on cadaver experiments and not real injury situations.