Comparison of stop-X and knee control training on side cut kinetics in futsal players with dynamic knee valgus: a randomized controlled trial.

Non-contact anterior cruciate ligament injuries are a persistent problem in soccer and futsal, and one recognized risk factor is dynamic knee valgus, where the knee collapses inward during side-cutting movements. This trial asked whether two different training approaches, called Stop-X and knee control training, could change knee alignment and landing forces in futsal players who showed this inward-knee pattern. Forty-five male players were randomly split into a Stop-X group, a knee control group, and a control group that did not train.

Both training groups showed a reduction in dynamic knee valgus and changes in ground reaction forces during a side-cut movement compared to before training, including increases in vertical and side-to-side forces and a shift in where pressure was centered under the foot. The two training methods appeared to work similarly well, though the study did not directly determine whether one outperformed the other. The main limitation is the small sample size split across three groups, and the outcomes measured were movement and force patterns rather than actual injury rates, so it remains unclear whether these changes translate into fewer ACL injuries.

If you play soccer or futsal, you may have heard that the way your knee moves when cutting or changing direction sideways can affect your risk of a serious knee ligament injury, specifically the anterior cruciate ligament. Researchers looked at whether two training programs, called Stop-X and knee control training, could help players whose knees tend to cave inward during these side-cutting movements. Forty-five male futsal players were divided into three groups: one did Stop-X training, one did knee control training, and one did no special training.

Both training groups showed improvement in knee alignment and changes in the forces measured as their foot hit the ground, compared to how they moved before training. The two programs seemed to work in similar ways, though the study did not directly compare them against each other. This was a small trial, and it measured movement patterns and forces, not whether players actually experienced fewer injuries.

So while the findings are promising for understanding how training might improve knee mechanics, they do not yet tell us whether either program reduces real-world injury risk.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This randomized controlled trial compared Stop-X training, knee control training, and a non-training control group in 45 male futsal players with observed dynamic knee valgus, with 15 participants per group. Outcomes were dynamic knee valgus (measured via camera and Kinovea software) and ground reaction force variables during a side-cut task, captured with a force plate. Both training groups showed a statistically significant reduction in dynamic knee valgus (P = 0.001, η²p = 0.760), along with increased vertical ground reaction force (P = 0.001, η²p = 0.691) and medial-lateral force (P = 0.038, η²p = 0.132), and a decrease in the mediolateral center of pressure (COPx) (P = 0.007, η²p = 0.227).

The abstract indicates both training protocols produced comparable improvements, but it does not report a direct head-to-head statistical comparison establishing superiority of one over the other. Key limitations include the small per-group sample size (n = 15), which restricts generalizability and power to detect between-group differences, and the reliance on kinetic and kinematic surrogate markers rather than actual injury incidence. Adverse events were not reported.

These findings should be interpreted as evidence of within-group biomechanical change associated with training exposure, not as proof of reduced injury risk.