Development of a Stability Criterion for Men's Basketball Shoes During Mediolateral Cutting Maneuvers

Ankle and knee injuries are common in court sports such as basketball and tennis, where there is an emphasis on cutting maneuvers and cleats are not a viable footwear solution. Such maneuvers generate substantial lateral ground reaction forces with the potential to overcome native anatomic ankle stability. The goal of this study was to develop a simple criterion that could be applied to assess the design of basketball shoes in an effort to enhance ankle stability and subsequently reduce lower extremity injuries. The criterion relates the foot's vertical force (F_v) and mediolateral force (F_ml) to the sole and wall thicknesses of the shoe through a critical ratio $\frac{F_{v}t}{F_{\mathrm{ml}}h}$ , where a critical ratio of is less than 1 denotes shoe instability. To evaluate our proposed criterion, a closed-form analysis combining force data from cutting movements characterized in previously published studies with simple geometric measurements of modern basketball shoes was conducted in nine shoe models. In addition, an experimental evaluation using a custom-built ankle model was carried out to validate the criterion on two of the shoe models. The ankle model included a prosthetic foot, steel shaft, double-U-joint, and load cell readout to acquire force and center of pressure associated with mediolateral ankle tipping. The experimental evaluation supported the validity of the instability envelope. Of the nine currently available shoe models evaluated here, none passed the criterion for all of the previously reported loading conditions and two demonstrated fundamental instabilities at the forefoot or heel.