A postural program to reduce dynamic knee valgus during single-limb squatting in young athletes: a preliminary study

Background: Dynamic Knee Valgus (DKV) is an undesirable multi-joint movement pattern associated with anterior cruciate ligament injury and patellofemoral pain syndrome, especially in sport activities. We assessed DKV in young athletes who followed a postural program to reduce a posterior rigidity mostly attributable to the tightness of hamstring muscles. Methods: We considered 12-18-year-old athletes that followed a six-week program simply based on hamstring stretching and abdominal muscle activation/strengthening. DKV was assessed during a single-limb squat and the frontal plane projection angle (FPPA) between the femur and tibia was considered. Results: Sixty-six athletes with a significant DKV (FPPA>=10°) were identified. Twenty-one subjects exhibited the considered rigidity profile and completed the intervention program. The mean reduction of the FPPA after the intervention was 8.1° (±7.9°), significantly asymmetric y about 3° (p<0.005) and skewed towards larger negative differences. The average change from the initial condition of -37% (±25%) was statistically significant (p=1.7x10-6). Conclusions: This preliminary result suggests that working on enhancing posterior muscle chain flexibility could be effective in reducing DKV in young athletes with a marked tightness of hamstring muscles. Moreover, this simple postural program can be a candidate for inclusion in sport training as a protective strategy against knee injuries.