of Drop Jumps and Sport-Specific Sidestep Cutting

Implications for Anterior Cruciate Ligament Injury Risk

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