Comparison
of Drop Jumps and Sport-Specific Sidestep Cutting
Implications for Anterior Cruciate Ligament Injury Risk
Screening
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].
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.
(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.)?
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
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?
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!
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.
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.
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.
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.
I also believe sport specific testing is ideal for any injury screening. I think drop landing tests have their place in functional testing, but as Brandon said, should be used as a tool in the large spectrum of testing. As far as cutting as an assessment for injury risk, I would be very interested to see if a study could investigate muscle activation during the cutting motion to determine imbalances in agonist v. antagonists, limb v. limb, sport v. sport, etc. It all comes back to understanding how each athlete's body adjusts to the wear and tear of their sport. Overall, an insightful and very interesting study.
Tricia,
Also a very interesting comment. I agree that a study looking at muscle activation during cutting would be very interesting to clinicians. I would also be careful to look at the testing procedure though to best mimic the motions of competition as well as accounting for variations in playing surface.