JOURNAL OF SPORTS SCIENCE & MEDICINE
ALTERATIONS OF KINETIC CHARACTERISTICS IN STEP UP AND OVER TEST IN PATIENTS WITH ANTERIOR CRUCIATE LIGAMENT DEFICIENCY
Hsiu-Chen Lin1,2, Horng-Chaung Hsu3,4, Chia-Ming Chang2, Pei-Wen Chiou4,5 and Tung-Wu Lu1
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C., 2Department of Physical Therapy, China Medical University, Taichung, Taiwan, R.O.C., 3Department of Orthopedics, China Medical University Hospital, Taichung, Taiwan, R.O.C., 4Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan, R.O.C., 5Department of Rehabilitation, Lotung Poh-Ai Hospital, Yilan, Taiwan, R.O.C.
© Journal of Sports Science and Medicine (2010) 9, 472 - 479
The purpose of this study is to investigate the alterations of kinetic characteristics in the step up/over test in patients with acute and chronic anterior cruciate ligament (ACL) deficiency. Twenty acute, twenty chronic ACL-deficient (ACLD) patients, and forty healthy controls participated in this study. The step up/over test was performed on a clinical force platform system to obtain the following variables: movement time, lift-up index and impact index. The percentages of the indexes from the stepping leg and time of step-up and swing- over were further calculated. These variables were examined statistically by using mixed repeated measure analysis of variance to reveal the differences between groups and between limbs. Smaller lift-up forces and longer swing-over time in both ACLD groups than those in the control group were found. One exception was the lift-up index in the affected side condition of the acute ACLD group, which was not significantly different from the controls. A reduced contribution to the impact index from the affected stepping leg was also found in the acute ACLD group. The acute ACLD group showed no significant change in their step-up strategy at the affected limbs, but they may have a poorer eccentric control of the affected knees on the step and thus put a larger portion of loading onto the unaffected landing leg. Our results indicated the lift-up index, swing-over time and load- distributing strategy at impact may be important parameters in monitoring functional recovery in patients with ACL deficiency. The detected alterations in these parameters could be used as a reference to design proper rehabilitation exercises for these patients.
Key words: Knee, ACL deficiency, kinetics, locomotion, step activity.
Anterior cruciate ligament (ACL) plays an important role in maintaining
anterior knee stability. However, it is unfortunately the most frequently
injured structure of the knee joint, especially for sports persons (Noyes
et al., 1980).
Altered kinetics and kinematics in lower extremities during walking, running,
cutting and stair climbing in patients with ACL deficiency have been observed,
such as smaller knee extensor moments and flexion angle during stance.
(Czerniecki et al., 1988;
Berchuck et al., 1990;
Patel et al., 2003;
Thambyah et al., 2004;
Waite et al., 2005).
A study on the natural course of functional recovery after ACL rupture
has suggested that returning to near normal levels in gait and hopping
may take 5 months in average (Button et al., 2005).
Nevertheless, the patients with chronic ACL deficiency (with an injury
duration of more than one year) have also been reported have impaired
functional performances (Barber et al., 1990;
Berchuck et al., 1990;
Patel et al., 2003;
Button et al., 2005;
Lindstrom et al., 2010).
Some of the altered functions were even suggested to be due to central
adjustments of motor control (Gauffin et al., 1990).
Therefore, patients with ACL deficiency could be further divided into
copers, non-copers and adapters by functional outcomes (Button et al.,
The non-copers demonstrated significantly poorer performances than the
copers in gait, hopping and step task (Rudolph et al., 2000;
Rudolph and Snyder-Mackler, 2004;
Button et al., 2008).
These studies demonstrated that functional recovery for patients with
ACL deficiency could be diverse and thus implied that careful monitoring
of functional retraining was essential before returning to sport activities.
and data acquisition
design and testing procedures
of the kinetic and temporal variables
scores and activity levels
distribution between legs
This study aimed to investigate the kinetic changes in performing
the step up/over test in patients with acute and chronic ACL deficiency.
This test was performed on the clinical force platform system and several
temporal and kinetic parameters from the system were obtained to represent
general performances in different subject groups. The control subjects
had comparable mean value in movement time (1.47 ± 0.30 sec) with those
in previous studies (Chmielewski et al., 2002;
Mattacola et al., 2004).
One of the previous studies did not find significant difference in movement
time between the acute ACLD group and control group (1.49 ± 0.24 sec),
but slightly longer movement time (1.63 ± 0.29 sec) in the unaffected
side condition (Chmielewski et al., 2002).
Our ACLD participants used slightly more time in both affected and unaffected
side conditions (1.70 ± 0.38 sec and 1.80 ± 0.39 sec respectively) than
the finding in the previous study and also demonstrated significantly
longer when compared with the control group (Figure
3a). These results indicated that our ACLD participants may be more
conservative in performing strenuous activities than those in the previous
study. Moreover, the decreases in exercise participation and functional
score for these patients after ACL rupture showed that the injury caused
significant impacts on their sport-related and functional abilities. The
step up/over test involved the activities used frequently in daily life
and can be used to evaluate the functional ability for patients with lower
limb pathology. Unlike hopping or running that may involve patients' maximal
exertion, the step up/over test is simpler and less risky for patients
with ACL deficiency. To perform stepping up/over, it was essential to
have skilled control of weight shifting between limbs and to have sufficient
muscle strength in concentric and eccentric contractions. The longer movement
time in both acute and chronic ACL groups suggested that the adaptation
may occur soon after ACL injury. The difference in movement time resulted
mostly from the slower swing-over suggested that the adaptation strategy
could be different in the step-up and swing-over during the step up/over
activity. This study demonstrated certain altered characteristics in the
different parts of the step up/over test for these patients. Therefore,
in this study, the test was divided into two phases to discuss the different
functional alterations. Additional parameters from the ground reaction
force data were extracted to understand the composition of this task and
the kinetic contribution from each leg.
The results of this study demonstrated the kinetic changes in the patients with acute and chronic ACL deficiency. The major changes in the step up/over test were shown in the lift-up index and the time of swing-over. Alteration of load-distributing strategy between limbs was found only in the acute ACLD group when descending from the step. Therefore, the lift-up index, the time of swing-over and load- distributing strategy at impact could be important parameters in indentifying functional impairments for patients with ACL deficiency. This study confirmed that the step test on the clinical force platform system could provide information in the recovery of the functional ability of the lower limb. The detected changes in these parameters could be used as a reference to design proper rehabilitation exercises for the patients with ACL deficiency.
The authors gratefully acknowledge the financial support of the National Health Research Institutes (NHRI-EX93-9126EP) and the National Science Council (NSC95-2314-B-039-018-) of Taiwan.
Employment: Lecturer, Department of Physical Therapy,
Degree: PT, PhD
Research interests: Biomechanics, rehabilitation, sports injury
Employment: Director, Department of Orthopedics,
Research interests: Orthopedics, sports injury
Employment: Research assistant, Department of Physical Therapy,
Degree: BS, PT
Research interest: Biomechanics, rehabilitation
Employment: Physical therapist, Department of Rehabilitation,
Degree: MS, PT
Research interests: Biomechanics, rehabilitation
Employment: Professor, Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.
Degree: Phil. D
Research interests: Biomechanics, motion analysis, rehabilitation engineering