Footwear traction and lower extremity joint loading.

BACKGROUND: Traction is influenced by the sole architecture and playing surface, with increases in traction potentially leading to injury. The mechanism as to how or why increased traction could lead to injury remains unknown.

PURPOSE: This study was undertaken to determine how shoes of different sole designs and traction influence knee and ankle joint moments.

STUDY DESIGN: Controlled laboratory study.

METHODS: Traction testing was performed on 2 shoes of varying sole designs (tread vs smooth) using a robotic testing machine. All testing was conducted on a 60-cm x 90-cm piece of sample track surface. Kinematic and kinetic data were then collected on 13 recreational athletes performing running V-cuts in the 2 different shoe conditions. Five trials per condition were collected with reflective markers placed on the right shank and shoe of each participant. Kinematic and kinetic data were collected using an 8-high-speed camera system and force plate.

RESULTS: The coefficient of translational traction and the peak moment of rotation were both significantly higher in the tread shoe compared with the smooth shoe (1.00 vs 0.87 and 23.87 N.m vs 16.12 N.m, respectively). The high-traction shoe had significantly higher peak ankle external rotation moments (89.58 N.m vs 80.17 N.m), peak knee external rotation moments (36.23 N.m vs 32.02 N.m), peak knee adduction moments (224.0 N.m vs 186.8 N.m), and knee adduction angular impulse (2.10 Nms vs 1.83 Nms) compared with the low-traction shoe.

CONCLUSION: Increased shoe traction significantly increased ankle and knee joint moments during a V-cut. Despite the significant difference in traction, no difference in performance was observed. These changes could have an effect on ankle and knee joint injury.

CLINICAL RELEVANCE: Shoes with decreased traction could be used in sports to reduce the joint moments in the knee and ankle and potentially reduce injury without a loss in performance.