Association of medial arch support of foot orthoses with knee valgus angle at initial contact during cutting maneuvers in female athletes: a controlled laboratory study

Background: The effect of medial arch support foot orthoses on kinematics and kinetics of the knee joint has remained unknown. Methods: Sixteen female collegiate-level athletes volunteered to participate. Participants were asked to perform a 30 degrees sidestep cut using orthoses of 3 different medial arch heights, comprising of the following: (1) "low," a full flat foot orthosis without arch support, (2) "mid," a commercially available foot orthosis with general height arch support, and (3) "high," a foot orthosis with double the commercially available height for arch support to observe the effect on the knee when overcorrected. Kinematics and kinetics of the knee joint were collected by a markerless motion capture system with 2 force plates and compared between orthosis types using linear regression analysis, assuming a correlation between the measurements of the same cases in the error term. Results: The knee valgus angle at initial contact was 2.3 +/- 5.2 degrees for "low" medial arch support height, 2.1 +/- 5.8 degrees for "mid," and 0.4 +/- 6.6 degrees for "high". Increased arch support height significantly decreased the knee valgus angle at initial contact (p = 0.002). Other kinematic and kinetic measurements did not differ between groups. Conclusions: The valgus angle of the knee at initial contact was decreased by the height of the medial arch support provided by foot orthosis during cutting manoeuvres. Increasing the arch support height may decrease knee valgus angle at initial contact. Medial arch support of foot orthosis may be effective in risk reduction of ACL injury.