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Sidestep cutting maneuvers in female basketball players: Stop phase poses greater
risk for anterior cruciate ligament injury
Di Xie ⁎, Yukio Urabe, Jyo Ochiai, Eri Kobayashi, Noriaki Maeda
Department of Sports Rehabilitation, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-Ku, Hiroshima 734-8553, Japan
Received 24 October 2011
Received in revised form 25 June 2012
Accepted 8 July 2012
Anterior cruciate ligament injury
Sidestep cutting maneuver
Background: Many non-contact anterior cruciate ligament (ACL) injuries in female basketball players occur
during sidestep cutting. The objective of this study was to identify the phases of a sidestep cutting maneuver
that place athletes at a greater risk for ACL injuries.
Methods: Ten healthy female collegiate basketball athletes were asked to perform sidestep cutting movements;
the knee ﬂexion and valgus angles as well as the electromyographic activity of the vastus lateral, vastus medial,
biceps femoris, and semimembranosus muscles of the non-dominant leg were analyzed during the maneuver.
Results: The mean knee valgus angle peak tended to be greater during the stop phase than during the
side-movement phase. The quadriceps activation during the stop phase was signiﬁcantly higher than that dur-
ing the side-movement phase. Moreover, the ratio of hamstring to quadriceps muscle activation during the stop
phase was signiﬁcantly lower than that during the side-movement phase, as assessed by surface electromyog-
Conclusion: Female basketball athletes have a higher risk for ACL injury during the stop phase than during the
side-movement phase of the sidestep cutting maneuver.
Level of evidence: Level III.
© 2012 Elsevier B.V. All rights reserved.
Non-contact anterior cruciate ligament (ACL) injuries commonly
occur during stopping, landing, and cutting maneuvers during basketball
drills and competitions .Bodenetal. reviewed videotapes of ACL
disruptions and noted that most non-contact injuries occur with the
knee close to extension during a sharp deceleration or landing maneu-
ver. However, anterior drawer load in isolation was insufﬁcient to rup-
ture the ACL without additional valgus load . In addition, knee joint
valgus is often implicated as a hazardous position for the ACL [4,5] and
has been linked to ACL injury risk .
Urabe et al.  performed electromyographic (EMG) analysis during
jump landing and demonstrated that the ratio of hamstring to quadriceps
muscle activation (H/Q ratio) was signiﬁcantly lower in female athletes
even though the knee ﬂexion angle was increased compared to that in
the early phase of landing. Anterior tibial translation and ACL strain are in-
creased among female athletes with a low H/Q ratio . The low H/Q ratio
could be one of the reasons female athletes have a higher incidence of
non-contact ACL injury during jump landing .Colbyetal. analyzed
quadriceps and hamstring muscle activity during sidestep cutting and
demonstrated that the H/Q ratio was the lowest when the knee ﬂexion
angle was 33°. Their study suggested that the risk of ACL injury is higher
at this angle.
Ireland  reported an example of an ACL injury to the left knee as
seen from the back and left side of a basketball athlete. In that particular
case, the subject had just rebounded and stopped to change direction to
avoid the defending player. However, in this situation, the injury is not
detected until the athlete takes his or her weight off the injured leg .
The body's center of mass moves laterally after one-legged jump landing
or stopping during sidestep cutting maneuvers. Therefore, knee valgus
and ﬂexion during these three maneuvers favor ACL injury. Based on
the potential mechanism of ACL injuries during sidestep cutting maneu-
vers, the phases at greater risk for ACL injury may be clariﬁed by analyzing
the knee ﬂexion angle on the sagittal plane, the knee valgus angle on the
frontal plane, and EMG activation of quadriceps and hamstring muscles.
Thus far, however, few studies have been conducted from the viewpoint
of kinematics and EMG variables during sidestep cutting.
The objective of this study was to identify the phases of a sidestep cut-
ting maneuver that put basketball athletes at a greater risk for ACL injuries
by analyzing knee valgus and ﬂexionanglesaswellasthequadricepsand
hamstring activity. We hypothesized that larger knee valgus angles,
smaller knee ﬂexion angles, and lower H/Q ratios will appear during de-
celeration phases of sidestep cutting with greater risk of ACL injury.
Ten healthy female collegiate basketball athletes who reported no
orthopedic disease in their lower extremities provided written con-
sent to participate in this study. The subjects' average age, height,
The Knee 20 (2013) 85–89
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E-mail address: firstname.lastname@example.org (D. Xie).
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weight, and history of playing basketball were 20.9±2.0 years,
158.4±7.0 cm, 52.8 ± 5.9 kg, and 5.1 ± 0.7 years, respectively. The
power for each analysis of variance was not less than 0.65 if the effect
size was more than 0.80 . A priori power analysis by G*power re-
vealed that obtaining a static power of 0.75 at an effect size of 0.80
with an alpha level of 0.05 required a sample size of at least 10 sub-
jects. Approval for this study was obtained from the institutional re-
view board of the Graduate School of Health Sciences, Hiroshima
University (ID number, 1027).
Four markers were placed on the ﬂoor 1 m away from each other. An
electric metronome was set at 180 beats/min, and the participant was
instructed to begin running on the ﬁrstbeep.Theparticipantrantwo
steps forward, planted the non-dominant leg on her third step, and
then the dominant leg stepped at an angle of approximately 90°. The
dominant leg was deﬁned as the leg usually used for kicking a soccer
ball . In this study, all of the participants indicated the right leg as
their dominant leg. The non-dominant leg was adopted as plant leg
based on the fact that the majority of surgical limbs in ACL reconstruction
are non-dominant . A cutting trial was deemed successful if the par-
ticipant performed the maneuver at a speed of 2–3m/s.Fivetrialswere
performed after sufﬁcient practice runs. Fig. 1 shows the protocol used
for sidestep cutting. The stop phase was deﬁned as the period from initial
foot strike to the maximum knee ﬂexion. The side-movement phase was
deﬁned as the period from maximum knee ﬂexion to toeing off. To sim-
ulate the actual basketball movements, participants were asked to place
their upper limbs in front of their chests as if they were receiving a pass.
Sixteen retro-reﬂective adhesive backbone markers (10 mm in di-
ameter) were placed over the anterior superior iliac spine, posterior
superior iliac spine, lateral and medial condyles of the femur, lateral
and medial condyles of the tibia, and lateral and medial malleoli be-
fore measurement. Three high-speed (200 frames/s) CCD cameras
(Has-200R; Ditect, Tokyo, Japan) were placed at the front and lateral
sides of the subjects to measure the knee ﬂexion angle from the sag-
ittal plane and the valgus and varus angles from the frontal plane dur-
ing sidestep cutting.
The raw kinematic data were ﬁltered using a General Cross Validatory
quintic-order spline  and analyzed using Dipp-Motion XD software
(Ditect, Tokyo, Japan). For quantiﬁcation of knee joint angles during
the cutting cycle, a kinematic model was deﬁned from a standing static
trial and from lower limb anthropometric measurement. The hip joint
center was estimated from the markers of anterior superior iliac spine
and posterior superior iliac spine according to Vaughan's method .
Joint centers for the knee and ankle were determined in the standing
trial .Thefemurcenterwasdeﬁned as the midpoint between the lat-
eral and medial condyles of the femur. The tibia center was deﬁned as
the midpoint between the lateral and medial condyles of the tibia. The
talocrural joint center was deﬁned as the midpoint between the lateral
and medial malleoli. Knee ﬂexion angles and valgus angles were calculat-
ed in the order xyz axes according to Grood's method  after two skel-
etal segments (thigh and tibia) were built.
Bipolar superﬁcial EMG sensors (Blue Sensor; MEDICOTEST, Olstykke,
Denmark) were placed over the vastus lateral (VL), vastus medial (VM),
biceps femoris (BF), and semimembranosus (SM) muscles on each
subject's non-dominant leg, following Perotto's method  before
EMG measurements. Maximal muscle activity was measured during a
maximum voluntary isometric contraction (MVIC) against a manual re-
sistance for 5 s . The MVIC tests for the VL and VM oblique muscles
were performed while the subject was in a sitting position with the
knee ﬂexed at 90°. The MVIC tests for the BF and SM oblique muscles
were performed while the subject was in a prone position with the
knee ﬂexed at 30°. Raw dynamic EMG and EMG gathered during
MVIC were ampliﬁed (Bio-amp ML132; AD Instruments, Colorado,
USA), subjected to A/D conversion at 1 kHz, and rectiﬁed with a
high-pass ﬁlter at 500 Hz and low-pass ﬁlter at 20 Hz (Mac Lab/8s;
AD Instruments, Colorado, USA). Then, the data were stored on a per-
sonal computer. Kinematic and EMG data were synchronized using a
digital timing signal counter (custom-made) and recorded using CCD
camera software (Ditect).
To allow for comparison of EMG intensity between phases, EMG
obtained during the sidestep cutting maneuver was normalized to
Fig. 1. Sidestep cutting withup to two approach steps and one leg stopping followedby sidestepping. This movement is observedfrom the anterior(above) and lateral aspects (below). A:
Initialcontact of the leftfoot. B: Maximum ﬂexionof the left knee.C: Left foot toeing off whileright foot sidesteps. The stopphase is from A to B,and the side-movement phaseis from B to C.
86 D. Xie et al. / The Knee 20 (2013) 85–89
Author's personal copy
the EMG acquired during an MVIC (%MVC). For the MVIC, the rectiﬁed
EMG signals were integrated every second, and the highest second
of muscle activation (representing 100% EMG activity) was used.
Quadriceps and hamstring muscle activation were calculated using
the method described by Kvist and Gillquist . Quadriceps muscle
activation was calculated as the average of VL and VM muscle activa-
tions. Hamstring muscle activation was calculated as the average of
BF and SM muscle activations.
Average values from ﬁve trials were used for analysis. The statisti-
cal analyses were performed using the Statistical Package for the So-
cial Sciences version 12.0J for Windows. Quadriceps muscle activity,
hamstring muscle activity, and H/Q ratios between the stop and
side-movement phases were compared using paired samples t-test.
Student's t-test was used for the comparison of knee valgus angle
peaks between the stop and side-movement phases. The level of
probability accepted as the criterion for statistical signiﬁcance was
The mean knee ﬂexion angle at the time of footstriking was 30.0± 7.4°,and the mean
maximum knee ﬂexion angle during sidestep cutting was 64.7±8.3°. The temporal
changes in knee valgus and varus angles for all 10 subjects formed a bimodal curve with
one valgus angle peak during the stop phase and another during the side-movement
phase (Fig. 2). The stop phase lasted 127.1± 26.5 ms, and the side-movement phase
lasted 156.3±23.8 ms. The ﬁrst knee valgus angle peak was observed at 79.6± 38.2 ms
when kneeﬂexion angle was 56.3±9.9°. The second knee valgusangle peak was observed
at 170.6± 33.7 ms when knee ﬂexion angle was 58.6±11.7°. The ﬁrst and second knee
valgus angle peaks were 11.7±7.57° and 9.1± 3.5°, respectively. The difference between
the ﬁrst and second valgus angle peaks was not signiﬁcant (Table 1).
Three of the 10 subjects presented only one knee valgus angle peak during the stop
phase but no knee valgus angle peak during the side-movement phase (Fig. 3). The
stop phase lasted 128.6±36.7 ms, and the side-movement phase lasted 160.0 ±
27.5 ms. The mean knee valgus angle peak of 19.5 ±10.3° was observed at 128.2±
29.1 ms when the knee ﬂexion angle was 60.2 ±11.3°.
There was a signiﬁcant difference for quadriceps muscle activity between the stop
and side-movement phases (pb0.05) (Table 1). The H/Q ratios during the stop and
side-movement phases were 0.32±0.13 and 0.89± 0.07, respectively; and the H/Q ratio
during the stop phase was signiﬁcantly lower than that during the side-movement
phase (pb0.05) (Table 1). In addition, the quadriceps muscle activity was approximately
112% MVC higher than that of the hamstring during the stop phase.
In 90° sidestep cutting maneuvers, female basketball players
presented temporary changes in the knee valgus and varus angles.
Previous studies have analyzed sidestep cutting maneuver at a
cutting angle of 45°  or 30–40° . In this study, the cutting
angle of 90° was adopted based on the fact that the 90° sidestep cut-
ting is dangerous and frequently used in athletic events. Regarding
another aspect of sidestep cutting, Olsen et al.  observed that
the sequence of events leading to a right-sided ACL injury included
the following: (i) the subject takes two steps with the ball and (ii)
pushes off to prepare for a sidestep cutting at high speed. Before our
measurements, sufﬁcient practice runs were performed to assure
that the participants could gain a high speed of 2–3 m/s.
In the report by McLean et al., subjects performing sidestep cutting
at 4.5–5.5 m/s showed a bimodal curve with two knee valgus angle
peaks . However, the two knee valgus angle peaks were not com-
pared, although a single value for the maximum knee valgus angle of fe-
male athletes was presented (14.2± 5.2°). In the present study, we
divided sidestep cutting stance time into stop and side-movement
phases and demonstrated that the mean knee valgus angle peak during
the stop phase was 11.7°, which was greater than the 9.1° found during
the side-movement phase. Nevertheless, these angles were smaller
than those reported in the study by McLean et al.
In this study, three of the 10 subjects presented only one knee val-
gus angle peak. Beaulieu et al. analyzed the changes in knee varus and
valgus angles during sidestep cutting with an approach speed of
4.0–5.0 m/s and similarly showed that only one knee valgus angle
peak (15.3±8.8°) was formed in female athletes . The maximum
knee valgus angle for the non-dominant side of females during land-
ing had been previously reported to be 12.5 ±2.8° . In the present
study, the mean knee valgus angle peak during the stop phase for the
subjects who exhibited only one knee valgus angle peak was 19.5 ±
10.3°, which was 4.2–5.3° greater than that reported previously.
Fig. 2. Temporarychanges of the knee varusand valgus anglesfor 10 subjects duringside-
step cutting. It is a bimodality curve with two valgus angle peaks. The ﬁrst valgus angle
peak was observed 79.6± 38.2 ms after foot striking during the stop phase. The second
peak was observed 170.6± 33.7 ms after foot striking during the side-movement phase.
The comparison of knee valgus angle peak, quadriceps muscle activity, hamstring mus-
cle activity, and H/Q ratio between the stop and side-movement phases.
Variable Stop phase Side-movement
p Effect size (r)
Knee valgus angle peak
11.7± 7.5 9.1 ±3.5 0.58 0.18
171.5± 50.0 69.9 ±50.1 b0.001⁎0.83
59.5± 28.3 53.0 ±35.7 0.66 0.15
H/Q 0.32± 0.13 0.89 ±0.07 b0.001⁎0.97
H/Q: The ratio of hamstring to quadriceps muscle activation.
Signiﬁcant difference between the stop and side-movement phases (p b0.05).
Fig. 3. Temporary changes of the knee valgus angles during sidestep cutting for the
three subjects. The mean knee valgus angle peak was observed 128.2 ±29.1 ms after
distal foot striking during the stop phase.
87D. Xie et al. / The Knee 20 (2013) 85–89
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McLean et al.  reported that the increased knee valgus angle
found in female athletes during sidestep cutting maneuvers is the
dominant risk factor for ACL injury. A previous study indicated that
ACL injuries occurred when the knee valgus angle was 5–20° during
sidestep cutting . The possibility of ACL injuries may be increased
during the stop phase because the knee valgus angle peaks during the
stop phase tend to be greater than those during the side-movement
phase. In fact, valgus restriction of the knee during sports maneuvers
can be expected to reduce the strain on the ACL , ultimately re-
ducing the number of non-contact ACL injuries . Interestingly, in
this study, the subjects with two knee valgus angle peaks ﬁrst landed
on their heels. On the other hand, subjects with only one knee valgus
angle peak ﬁrst landed on the distal foot (Fig. 4). However, the two
landing techniques were not compared because of the small number
of subjects in each group. The relationship between knee joint move-
ment and the two different types of landing (heel versus distal foot)
should be monitored and analyzed carefully in the future.
A previous study revealed that the H/Q ratio of female athletes
was 0.25–0.28 during jump landing . In the present study, the av-
erage H/Q ratio of the stop phase was 0.32±0.13, similar to that
reported previously. In addition, a previous study  demonstrated
that the H/Q ratio was the lowest when the knee ﬂexion angle was
33°. At that angle, the quadriceps muscle activity was greater than
that of the hamstrings by about 80% MVC. We assumed that any mus-
cle activity of the quadriceps exceeding that of the hamstrings by 80%
MVC was a risk factor for ACL injury during sidestep cutting. In this
study, the muscle activity of the quadriceps was 112% MVC higher
than that of the hamstrings during the stop phase, which supports
our hypothesis. The low muscle activity of the hamstrings during
the stop phase may be insufﬁcient to prevent anterior tibial transla-
tion, resulting in an increased risk of ACL injury.
Krosshaug et al.  demonstrated that the estimated time of ACL
injury, based on the group median, ranged from 17 to 50 ms after ini-
tial ground contact. A previous study reported that ACL injuries occur
during the early stage of the deceleration phase of sidestep cutting
cycle . The early stage of the deceleration phase was deﬁned as
the ﬁrst 20% of the period from the initial contact of the foot to toeing
off—the stage when the knee ﬂexion angle is less than 40°. In the
present study, the early stage of the deceleration phase during side-
step cutting was the period from the initial contact of the foot to
57 ms after foot striking, at which time the knee ﬂexion angle was
52.8° and the knee valgus angle was 6.6°. In addition, ACL injuries
were demonstrated to occur most commonly approximately 50 ms
after foot striking during landing in a simulation study . Koga et
al.  reported that all the handball and basketball players had im-
mediate valgus motion within 40 ms after initial ground contact.
Bencke et al.  found that the activity of the knee extensors peaked
at approximately 46 ms after toe contact, while the knee ﬂexors
showed a minimum EMG activity during sidestep cutting. The ﬁnd-
ings of the present study substantiates previous research [2,11,26]
that the early stage of the deceleration phase of sidestep cutting is as-
sociated with the greatest risk for ACL injury.
Certain limitations of this study should be addressed. First, 10 fe-
male participants were recruited and included in the analysis. The
Fig. 4. The different sidestep cutting maneuvers that create two valgus peaks (above) or only one valgus peak (below). The ﬁgure shows the maneuvers for the heel landing ﬁrst (A)
and the distal foot landing ﬁrst (B).
88 D. Xie et al. / The Knee 20 (2013) 85–89
Author's personal copy
small size of this group may have reduced the statistical power of the
ﬁndings. A more consistent and universal epidemiological study with
a large number of participants should be conducted in the future. Sec-
ond, the present study is an experimental study and does not complete-
ly simulate the actual sidestep cutting maneuver in real life basketball
competitions. Analysis of the aspects inﬂuencing sidestep cutting,
such as speed and direction of cutting, is necessary. Finally, the present
study only analyzed the non-dominant leg. A previous study reported
that the knee valgus angle peak of the dominant leg in female athletes
is signiﬁcantly greater than that of the non-dominantleg during landing
. We plan to examine the differences of the maximum knee valgus
angles and muscle activity of the non-dominant as well as the dominant
leg during sidestep cutting maneuvers in future studies.
The authors analyzed 90° sidestep cutting maneuvers for female
basketball players and discovered that the temporary changes in the
knee valgus and varus angles may present two valgus angle peaks
or only one peak. The knee valgus angle peak during the stop phase
tended to be greater than that during the side-movement phase. On
the contrary, the H/Q ratio during the stop phase was signiﬁcantly
lower than that during the side-movement phase. We concluded
that female basketball athletes have a higher risk of ACL injury during
the stop phase of sidestep cutting as compared to the side-movement
phase. In order to prevent ACL injury, there is a need to train ham-
string muscles, and knee valgus should be avoided, especially during
the stop phase of sidestep cutting.
Conﬂict of interest
None of the authors reports any conﬂict of interest.
No sponsor supported this study.
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