Comparison of Knee Kinematics during Anticipated and Unanticipated Landings

Tony Moreno PhD CSCSSchool of Health Promotion and Human PerformanceEastern Michigan University

Overview

Basketball – • In general, female high school participants incur knee injury rates

nearly twice as high as their male counterparts.

• Anterior cruciate ligament (ACL) injuries occur at a rate of approximately 1 in 65 per participant annually.

• ACL surgery rate nearly 4 times higher.

Soccer –• In general, female high school participants incur knee injury rates

approximately 2.5 times higher than their male counterparts.

• ACL surgery rate 3 times higher Hewett et al., 2006

Mechanism of InjuryIncidents are typically non-contact while the athlete is: • landing from a jump or,• conducting a pivoting or sidestep cutting-type

maneuver

Injury mechanism may involve:• Tibial rotation in opposition to a femoral

rotation,• concurrent with a valgus (knock-kneed)

stress at relatively low knee flexion angles,• while suddenly decelerating on a fixed or

planted foot.

Unpredictable landing and cutting movements are inherent characteristics within sport, with knee joint flexion (KJF) and time to peak knee joint flexion (TKJF) often associated with increased risk of lower extremity injury.

– What kinematic differences exist between anticipated and unanticipated jump landing conditions?

– Do injury prevention protocols address the indeterminate movement conditions observed in practice and competition?

PurposeThe purpose of this study was to compare kinematic parameters of

the knee during anticipated and unanticipated landing conditions among adolescent female basketball athletes performing a maximal vertical jump effort.

Statement of the Problem

Methods• Six adolescent female AAU basketball players (13.8 ± 0.4yr.; 62.7 ±

17.87kg; 1.66 ± 0.08m).

• Maximal vertical jump assessed for all participants with the use of a Vertec™ (Sports Imports, Columbus, OH).

• Participants performed a maximal vertical jump, landed and immediately sprinted either left or right with an anticipated (A) and unanticipated (U) direction upon impact.

Methods (continued)• Kinematic data collected at 120 Hz with 8 digital cameras and EvART

Version 4.2 software (Falcon, Motion Analysis Corporation, Santa Rosa, CA).

• Force data sampled at 1200Hz with an AMTI LG6 force platform (Advanced Medical Technology Incorporated, Watertown, MA) synchronized with the motion capture system.

• Kinetic data derived with MATLAB 7 software package (MathWorks, Nattick, MA, USA).

• A paired sample t-test was performed for each dependent variable to determine if significant differences (p< 0.05) existed between the anticipated and unanticipated landing condition.

anticipated landing

unanticipated landing

70.9

55.6

0

10

20

30

40

50

60

70

80de

gree

s

Anticipated

Unanticipated

Mean peak knee flexion

KJF (A=70.9 ± 10.2º; U=55.6 ± 12.7º)

0.2

0.17

0.15

0.16

0.17

0.18

0.19

0.2

0.21

seco

nds

Anticipated

Unanticipated

Mean time to peak knee flexion

TKJF (A=0.2 ± 0.06s; U= 0.17 ± 0.05s)

Results• Mean peak values for KJF (A=70.9 ± 10.2º; U=55.6 ± 12.7º) and

TKJF (A=0.2 ± 0.06s; U= 0.17 ± 0.05s) were significantly different (p<0.05) when comparing anticipated to unanticipated landing conditions.

• It is apparent subjects utilize different kinematic strategies with the unpredictable landing scenario.

• Conclusion: Evaluation of anticipated and unanticipated landings may be necessary to ensure injury intervention protocols provide adequate variability and unpredictability to attenuate factors associated with lower extremity injury.

Neuromuscular Factors

• Corrective responses via proprioceptive (sensory) feedback.

• Preplanning through the Central Nervous System.

• Physical training can potentially

change the neuromuscular response.

• Alteration of biomechanical factors may reduce the incidence or severity of injury.

Hewett et al., 2006

3.64

5.1

0

1

2

3

4

5

6I

x de

gree

s/s2 /b

ody

mas

s(kg

)

Anticipated

Unanticipated

Mean peak knee extensor moment on impact

PKJM (A= 3.64 ± 1.07 Nm/kg; U= 5.1 ± 1.4 Nm/kg)

unanticipated training

anticipated training

When comparing ACL injured subjects to controls performing similar movements with video analysis…

- …injured demonstrate a hind or flatfoot disposition on impact

- …non-injured exhibit greater plantar flexion on impact

- …injured demonstrate less knee flexion on impact

Boden, et al. (20009)

Future Research• Ankle joint kinematics (talar and subtalar) on landing, are

significantly associated with kinematic and kinetic measures of the knee

– Peak knee joint flexion– Time to peak knee joint flexion– Peak ground reaction force at impact– Eccentric knee extensor torques – Knee abduction/adduction torques– Relative loading rate at impact

These biomechanical parameters are strongly associated with ACL and lower extremity injury…

Future Research

• Select uninjured population at risk for ACL injury and currently participating in activities that include jumping and cutting.

• Determine the potential influence of ankle joint motion on knee joint kinematics and kinetics, while landing from a jump task.

• Perform jump task with both anticipated and unanticipated landing conditions.

• Expose experimental subjects to a training intervention (anticipated and unanticipated?) that may alter proprioceptive mechanisms.

• To test the hypotheses, compare pre- and post intervention biomechanical parameters within and between groups.

Thank You!

Tony Moreno PhD CSCSSchool of Health Promotion and Human PerformanceEastern Michigan Universityamoreno@emich.edu