Sports Medicine Research: In the Lab & In the Field: Comparing Screening Methods for ACL Injury Risk (Sports Med Res)
Wednesday, February 13, 2013

Comparing Screening Methods for ACL Injury Risk

Comparison of Drop Jumps and Sport-Specific Sidestep Cutting Implications for Anterior Cruciate Ligament Injury Risk Screening

Kristianslund E and Krosshaug T, Am J Sorts Med. 2013 January; [Epub Ahead of Print].

Non-contact anterior cruciate ligament (ACL) injuries occur across many different sports and have been shown to be linked to long-term degenerative joint changes. If we had a gold standard for clinically screening ACL injury risk then we could identify patients at high risk for an ACL injury and determine if prevention programs are having a desired effect on their biomechanics. Screening tests however focus on 2-legged and controlled jumps rather than sidestep cutting and single-legged landing which many ACL injuries occur during. Therefore, Kristianslund and Krosshaug performed a study to describe knee biomechanics in drop jumps and sidestep-faking maneuvers among elite female handball players. A total of 120 players (mean age of 22.4 years) performed sidestep cutting and drop jumps. When players performed the sidestep cutting task they ran down a 5 meter approach and then were told to perform their regular sidestep cut, trying to fake a static defender into going one way while cutting the other. A total of 3 cuts were analyzed. Drop jumps were performed using a 30 cm high box. Players dropped off the box and immediately performed a maximal jump. Both sidestep cutting and drop jumps were analyzed with 2 force plates and 8 infrared cameras. The authors calculated maximum knee abduction and knee internal rotation moments in the first 100 milliseconds after initial contact; maximum knee flexion moments during contact with the force plate; knee flexion, knee abduction, and knee internal rotation at initial contact; as well as maximum knee flexion, knee abduction, and knee internal rotation. Overall, knee biomechanics were different between drop jumps and sidestep cutting. Sidestep cutting exhibited greater valgus and internal rotational angles. Further, knee joint moments (loading) were higher in all 3 planes of motion, with knee abduction moments 6 times higher, in sidestep cutting than drop jumps.

The data presented in this study clearly demonstrates that 2 legged controlled drop jumps, which are typically used for ACL injury screening, are not consistent with the stresses placed on the knee joint during actual competition. This implies that sport-specific tasks, like sidestep-cutting tasks, may be more effective in identifying patients at risk for ACL injury. However, one should be wary that the study was performed in a laboratory setting against a static defender and did not assess whether the new task is actually more predictive of ACL injuries than drop jumps.  Another point of concern is the standardization of a sidecutting protocol. All athletes have preferred techniques of sidecutting, which may further affect the forces placed on the knee. This could be advantageous for identifying patients with high-risk techniques but could also make it more challenging for clinicians to implement as a screening test. Overall, this study provides clinicians with another step towards a gold-standard method of ACL injury screening which will inevitably require a task which mimics real-time competition situations for a specific sport. In the meantime, this study questions whether drop jumps, which are biomechanically distinct from cutting tasks, are an ideal method to screen patients for risk of ACL injury. Tell us what you think after seeing these results. Do you think sport-specific tasks (e.g., cutting tasks) will be better at predicting who is at risk for an ACL injury than drop jumps? Do you think new ACL injury screening tests should be sport-specific (i.e. basketball, baseball, football, etc.)?

Written by: Kyle Harris
Reviewed by: Jeffrey Driban

Related Posts:

Kristianslund E, & Krosshaug T (2013). Comparison of Drop Jumps and Sport-Specific Sidestep Cutting: Implications for Anterior Cruciate Ligament Injury Risk Screening. The American Journal of Sports Medicine PMID: 23287439

6 comments:

Nic Philpot said...

Kyle,
I really like the approach that y'all took with this study. While a drop jump can tell you certain things, I have long believed that it is not a good standard for calculating ACL injury risk. The amount of ACL injuries that occur non contact while applying a valgus or varus and rotational force on the knee is to high for us to simply be watching drop jumps to asses the risk of injury. I am a strong believer that when it comes to assessing injury risk, sports specific tasks are almost always better. This is because the forces applied will be much more realistic to the forces that the athlete will apply on their joints when they are on the field. I am interested to know if any of the athletes that were tested had a previous ACL injury, or any injury that made them miss a substantial amount of time in the past 3-6 months?

Kyle Harris said...

Nic,

Excellent comment! I agree that sports specific tests are critical. I checked the study again and you were 100% correct in your suspicion. The authors made no comment on whether or not past medical history or, more specifically ACL injury, was an exclusion factor. This would be a major limitation to the literature as we have evidence that knee kinematics is altered following ACL injury. If individuals with previous ACL injuries were included then that would greatly influence their results. Even further, previously ACL-injured athletes would also undergo extensive rehabilitation. This may lead to a bias to those who underwent landing training making them perform better than pre-injury. Great catch!

Becca Burkhart said...

With ACL injury screening I think that the sidestep-cutting tasks are more appropriate than drop jumps. Sidestep-cutting will stress the knee with more rotational forces, which is similar to how most non-contact ACL injuries occur. I wonder if the screening results would be different when comparing two different sports using the same sidestep cutting task. There are many differences when comparing the cutting that occurs in soccer to that which occurs in football. It would be interesting to see research using sidestep-cutting drills that were more sport specific.

Stephanie Michel said...

I think sports specific tasks are much more reliable than a drop jump. For example, doing a vertical jump test with a volleyball team could help determine, when jumping, which athletes tend to land with a genu valgum. If it is found that those athletes land with their knees knocked, a prevention program to strengthen certain areas can be done throughout the season. This could then help lead to a decrease in ACL tears.

Brandon Green said...

Sport specific tasks are ideal and I feel should be the gold standard, because they mimic movements that are seen in sports. Using just drop jumps for every athlete would not give reliable results for ACL risk athletes. Drop jumps could be utilized as a tool to assess but certainly can not be used as the gold standard. There must be the inclusion of cutting drills because my personal experience is athletes have non-contact ACL tears while sudden change of direction is involved.

Kyle said...

Becca, Stephanie, and Brandon,

You all make an excellent consensus. Yes, I too believe that the sport specific tasks should be used. This gives us a clinicians the best understanding of how well that specific knee will react during activity. With that being said, Stephanie, your point is well taken. While many see a drop jump test as non-sport specific, in certain situations, such as volleyball the drop jump could be very applicable. I think we should all keep in mind that the most dynamic activity may not always be the most sport specific activity. My question for the group would be in the case of a sport such as basketball which includes both jumping and cutting aspects, how do you think it would be best to proceed? Would you test position players differently? Would you use both tests for all players? If so, how could you get an overall picture how the knee would react? I would be very interested to hear your comments.

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