Changing How We Land to Reduce ACL Injury Risk Factors

Source: Shimokochi, Y., Ambegaonkar, J.P., Meyer, E.G. (2016). Changing Saggital-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia. Journal of Athletic Training, 51(9), 669-81.

Summary

This is an article that will require a bit of translation for the general reader, so I will do my best to put things in simplified terms.  Let me know if there is something that is still unclear.  In summary, the authors took that knowledge that forces on the tibia are believed to be the primary cause of ACL injury and decided to see if they could affect those forces during single-legged landing by changing the landing mechanics.   The three landing styles that they tested were self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL).

Research Conclusions:

  • During impact of single-legged landing, sagittal-plane related forces and body movements strongly affect the forces on the tibia and anterior cruciate ligament (ACL) injury risk. In other words, how we land on a single-leg affects our ACL injury risk.
  • To reduce harmful forces on the ACL, we should improve sagittal-plan landing mechanics.
  • LFL resulted in longer time to peak tibial axial forces, reduced ground reaction force (GRF), and a more posteriorly inclined GRF compared to URL (the worst) and SSL.  Translation: body leaning forward and landing on the toes resulted in less injurious forces on the ACL.

Clinical Pearls

  • We may be able to reduce ACL injury risk by analyzing single-legged landing mechanics and training athletes to land with the body leaning forward and landing on the toes (to create greater knee flexion and reduced forces on the ACL)

The Breakdown

Level of Evidence: 3b

This was a fairly small study (only 20 participants) that was applied to a relatively small portion of the population (20-somethings).  However, I like this study because it did not try to be something it is not: an end-all answer to ACL injury prevention.  Instead, it took one small component of non-contact ACL injury risk, single-legged landing mechanics, and narrowed down the confounding factors by limiting the sample to young, active participants.  If the sample was too large and included a broad range of ages, activity levels, and health factors, then a negative finding would not have given us any real information.  Instead, we can now look at the results and see that 1) we know that landing mechanics affects forces on the ACL and 2) how we perform a single-legged land seems to change those forces in this particular subgroup.  This does not mean that we can conclude that if we change how we land, then we can reduce the risk of ACL injury, but it does mean we now have a better grasp of how to assess that claim (and that it is a claim worth looking into).  The next steps would be to evaluate the outcomes of landing mechanics training on ACL injury and to continue testing biomechanical outcomes on a larger population that includes various ages, heights, weights, races, and sex balance.

PICOT Criteria

Population:  Twenty recreationally active participants – 10 men and 10 women (age = 23+/- 3.6 years, height = 171.0 +/- 9.4cm, mass=73.3+/-12.7kg)

Intervention: leaning forward and landing on toes, body upright with flat-footed landing

Comparison: self-selected landing

Outcome of interest: sagittal plane tibial inclination and knee flexion angles, ground reaction force magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces

Time: at peak force during ground contact

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