Journal of Electromyography and Kinesiology 22 (2012) 598–606

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Journal of Electromyography and Kinesiology

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Hip and knee joint kinematics during a diagonal jump landing in anteriorcruciate ligament reconstructed females

Eamonn Delahunt a,b,⇑, Anna Prendiville a, Lauren Sweeney a, Mark Chawke a, Judy Kelleher a,Matt Patterson a, Katie Murphy a

a School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Irelandb Institute for Sport and Health, University College Dublin, Dublin, Ireland

a r t i c l e i n f o

Article history:Received 3 July 2011Received in revised form 16 February 2012Accepted 16 February 2012

Keywords:KneeACLLigamentReconstructionBiomechanicsInjury

1050-6411/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.jelekin.2012.02.009

⇑ Corresponding author. Address: School of PubliPopulation Science, University College Dublin, HealDublin 4, Ireland. Tel.: +353 1 7166671.

E-mail address: eamonn.delahunt@ucd.ie (E. Delah

a b s t r a c t

Anterior cruciate ligament (ACL) injury is a common injury encountered by sport medicine clinicians.Surgical reconstruction is the recommended treatment of choice for those athletes wishing to returnto full-contact sports participation and for sports requiring multi-directional movement patterns. Theaim of ACL reconstruction is to restore knee joint mechanical stability such that the athlete can returnto sporting participation. However, knowledge regarding the extent to which lower limb kinematic pro-files are restored following ACL reconstruction is limited. In the present study the hip and knee joint kine-matic profiles of 13 ACL reconstructed (ACL-R) and 16 non-injured control subjects were investigatedduring the performance of a diagonal jump landing task. The ACL-R group exhibited significantly lesspeak knee joint flexion (P = 0.01). Significant between group differences were noted for time averagedhip joint sagittal plane (P < 0.05) and transverse plane (P < 0.05) kinematic profiles, as well as knee jointfrontal plane (P < 0.05) and sagittal plane (P < 0.05) kinematic profiles. These results suggest that aberranthip and knee joint kinematic profiles are present following ACL reconstruction, which could influencefuture injury risk.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Anterior cruciate ligament (ACL) rupture is a common injuryencountered by clinicians involved in the prevention, treatmentand rehabilitation of sports injuries. The ACL functions to providemechanical stability to the knee joint by providing restraint toexcessive anterior tibial translation as well as frontal and trans-verse plane movements (Andersen and Dyhre-Poulsen, 1997).The ACL, in addition to its role in providing mechanical stabilityto the knee joint also plays an integral role in knee joint sensorimo-tor control and proprioception (Johansson et al., 1991). Thus, rup-ture of the ACL can negatively influence knee joint function(Bonfim et al., 2003).

The aim of ACL reconstruction surgery is to restore knee jointmechanical stability such that the athlete can return to sporting par-ticipation. However, full restoration of knee joint function followingACL reconstruction is often limited, and future complications such asthe development of knee joint osteoarthritis (Chaudhari et al., 2008),future knee joint injury (Waldén et al., 2006) and re-rupture are ofparticular concern (Shelbourne et al., 2009).

ll rights reserved.

c Health, Physiotherapy andth Sciences Centre, Belfield,

unt).

Reports in the literature suggest that female athletes have ahigher incidence of non-contact ACL injuries when compared tomale athletes participating in the same sports (Agel et al., 2005;Waldén et al., 2011). A high proportion of ACL injuries in femaleathletes are non-contact in mechanism and occur during sportingactivities such as twisting, cutting and single-leg landing (Olsenet al., 2004; Krosshaug et al., 2007). Specific biomechanical mea-sures that have been reported to contribute to the ACL injurymechanism in female athletes include, an increased knee valgusangle, and decreased knee flexion range of motion (Myer et al.,2011). Furthermore, a recent model-based image-matching studyby Koga et al. (2010) indicated that ACL injury is characterizedby a low knee flexion angle during initial contact followed by asudden increase in knee joint valgus angular displacement.

Traditionally the success of ACL reconstruction has been as-sessed in terms of the anterior tibial translation (Daniel et al.,1985; Jonsson et al., 1993) and rotational laxity (Musahl et al.,2007; Lorbach et al., 2009) present following reconstruction. Thesemethods of assessment measure passive knee joint laxity and donot replicate the loading patterns experienced during dynamicfunctional activities. Recently numerous studies has examinedknee joint biomechanics during various activities such as walking(Butler et al., 2009; Gao and Zheng 2010) and pivoting tasks(Ristanis et al., 2005; Claes et al., 2011; Lam et al., 2011). Two more

40cm

60cm

A Start Position

A Finish Position

B Start Position

B Finish Position

Fig. 1. Diagram for diagonal jump to land set-up. (A) Start/finish position: this is thestart position for a single leg landing on the subjects’ left leg. The subject initiatesthe jump from single leg standing on their right leg at the ‘‘A start position’’. Theythen land on the centre of the force plate on their left leg at the ‘‘A finish position’’.(B) Start/finish position: this is the start position for a single leg landing on thesubjects’ right leg. The subject initiates the jump from single leg standing on theirleft leg at the ‘‘B start position’’. They then land on the centre of the force plate ontheir right leg at the ‘‘B finish position’’.

E. Delahunt et al. / Journal of Electromyography and Kinesiology 22 (2012) 598–606 599

recent studies have examined knee joint function during hoppingtasks (Gokeler et al., 2010; Deneweth et al., 2010). Landing froma jump places higher demands on the knee joint than walkingand is considered to be more representative of those demandsexperienced in sporting situations (McNair and Marshall, 1994;Decker et al., 2002). The majority of the aforementioned studieshave concentrated solely on knee joint biomechanics. There is anincreasing awareness in the literature of the influence of proximalstructures in the mechanism associated with ACL injury (Quatmanet al., 2010; Hashemi et al., 2010). Thus, the aim of the presentstudy was to investigate patterns of hip and knee joint angular dis-placement during a diagonal jump landing in a group of femaleathletes who had previously undergone ACL reconstruction. Theprimary hypothesis was that female athletes who had previouslyundergone ACL reconstruction, but who had since returned to fullsporting participation would exhibit altered hip and knee jointkinematic profiles, when compared to an age, sex and activitymatched control group.

2. Methods

2.1. Subjects

Thirteen recreational female athletes (age, 23.69 ± 3.11 years;height, 1.63 ± 0.05 m; body mass, 64.96 ± 9.01 kg; BMI, 24.23 ±2.34 kg/m2) who had previously undergone ACL reconstructionfor a non-contact ACL injury volunteered to participate. Seven ofthe athletes had surgical stabilization using a hamstring auto-graft,with the remaining athletes having had a bone-patellar tendon-bone auto-graft surgical procedure. The mean time from surgicalstabilization to the present study was 4.4 years. At the time of test-ing all athletes were fully engaged in field or court based sports(e.g. Gaelic football, soccer, hockey, basketball) at club or county le-vel and no athlete was undergoing any form of formal rehabilita-tion. All athletes subjectively reported having returned tosporting participation equivalent to that engaged in prior to injury.Sixteen recreational female athletes (age, 20.81 ± 1.16 years;height, 1.65 ± 0.06 m; body mass, 64.71 ± 7.05 kg; BMI, 23.72 ±2.46 kg/m2) without previous history of knee joint injury, volun-teered to participate as control subjects. All athletes played fieldor court based sports (e.g. Gaelic football, soccer, hockey, basket-ball) at club or county level. Before participation in the study allsubjects were required to read an information leaflet and sign aform consenting to participation in the study. The study was ap-proved by the University Human Research Ethics Committee.

2.2. Subjective knee questionnaires

All subjects were required to complete the IKDC (Risberg et al.,1999) questionnaire as well as the KOOS (Roos et al., 1998)subscales.

2.3. Kinematics

Kinematic data acquisition was made at 200 Hz using threeCODA mpx1 units (Charnwood Dynamics Ltd., Leicestershire, UK),which were fully integrated with four AMTI (Watertown, MA,USA) walkway embedded force-plates. The CODA mpx1 units weretime synchronized with the force-plates.

The following anthropometric data were obtained for the calcu-lation of internal hip, knee and ankle joint centers: the pelvic widthfrom the left anterior–superior iliac spine to the right anterior–superior iliac spine; the pelvic depth from the anterior–superioriliac spine to the posterior–superior iliac spine; the knee widthand the ankle width. The limb lengths of the thigh, the shank andthe foot were measured using a measuring tape, and body mass

and height measurements were also obtained. CODA infraredlight-emitting diode markers were attached to specific lower limbanatomical positions as outlined in the CODA mpx30 users manual.Wands with anterior and posterior markers attached were posi-tioned on the pelvis and sacrum, the thigh, and the shank in accor-dance with the manufacturer’s guidelines by the same investigatorfor all subjects. Furthermore markers were positioned on the lateralaspect of the knee joint line in the median frontal plane, the ante-rior aspect of the lateral malleolus, the posterior–inferior lateral as-pect of the heel and the lateral aspect of the fifth metatarsal head.The infrared light-emitting diode markers and associated batterypacks were fixed to the skin and the marker wands with double-sided adhesive tape. Previous work in our laboratory has showngood reliability of this specific set-up protocol for dynamic move-ment analysis (Monaghan et al., 2007), with this previous set-upalso being utilized for other motion analysis applications (Mona-ghan et al., 2006; Delahunt et al., 2006a,b; Delahunt et al., 2007).

2.4. Test protocol

For the execution of the diagonal jump to land, subjects stoodbare-foot in single-leg stance at the posterior lateral aspect of aforce-plate on the non-test leg. They were then required to performa diagonal jump to land on another force plate on the test leg(Fig. 1). Each subject performed three trials of the diagonal jumpto land. A trial was deemed successful if the landing occurred with-in the field of view of the motion analysis system, and if the subjectwas able to maintain their balance after landing. A trial wasdeemed unsuccessful if the subject touched the ground with theirnon-test leg, or if they shifted the position of their test leg on theforce-plate after landing. Unsuccessful trials were discarded andadditional trials were undertaken if necessary. Prior to the comple-tion of the test trials all subjects were allowed three practice trialsfor familiarization with the testing procedures, during which

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verbal feedback was provided by the investigators. The ACL recon-structed leg was used as the test leg in the ACL-R group. This re-sulted in seven left and six right ACL-R knees being tested. Anequal number of left and right legs were test in the control sub-jects. (i.e. 8 left and 8 right).

2.5. Kinematic analysis

The vertical component of ground reaction force (GRF) was uti-lized to identify the point of initial contact (IC) during landing,which was defined as the point when the vertical GRF first ex-ceeded 10 N (McLean et al., 2007).

Kinematic data were calculated by comparing the angular ori-entations of the co-ordinate systems of adjacent limb segmentsusing the angular coupling set ‘Euler Angles’ to represent clinicalrotations in three dimensions. Marker positions within a Cartesianframe are processed into rotation angles using vector algebra andtrigonometry (CODA mpx30 User Guide, Charnwood DynamicsLtd., Leicestershire, UK). Joint angular displacements were calcu-lated for the hip, and knee joints in the sagittal, frontal, and trans-verse planes. A neutral stance trial was used to align theparticipant with the laboratory co-ordinate system and to functionas a reference position for subsequent kinematic analysis as rec-ommended in previously published literature (Nester et al., 2003).

Kinematic data were analyzed using the CODA software. The200 ms time frame post-IC was extracted from each test trial. Eachtrial was normalized to 101 point periods representing the 200 mstime frame post-IC. The three normalized trials for each participantwere combined to create an average ensemble curve for each par-ticipant, with group profiles then being calculated (i.e. ACL-R sub-jects vs control subjects). The standard deviation for each datapoint on the average ensemble curve for each participant was calcu-lated before entry into the calculation of the average standard devi-ation for each group. The magnitude of the peak hip and knee jointangular displacements for each trial for each participant were com-bined to calculate an average value for each participant, prior to thecalculation of group average profiles. Similar methods of data anal-ysis have previously been described by Brown et al. (2012, 2009).

2.6. Statistical analysis

Between-subject ANOVA was used to test for group differencesin the IKDC and KOOS subscale scores. Associated effect sizes (etasquared) were calculated using the formula: sum of squares be-tween-groups/total sum of squares (Pallant, 2007) and quantifiedaccording to Cohen (1988) as 0.01 = small effect size, 0.06 = med-ium effect size, and 0.14 = large effect.

Between-subject ANOVA was used to test for between groupdifferences in magnitude of the peak hip and knee joint angulardisplacements. Associated effect sizes were also calculated asaforementioned (Pallant, 2007).

Time-averaged profiles for hip, and knee joint kinematics werecalculated for each participant, with group mean profiles thenbeing subsequently calculated. Differences in ACL-R and controlgroup time-averaged profiles were tested for statistical signifi-cance using independent two-sided t-tests for each data point.All data were analysed using Predictive Analytics SoftWare (Ver-sion 18, SPSS Inc., Chicago, IL, USA) with statistical significancebeing set at P < 0.05.

3. Results

3.1. Subjective knee questionnaires

ACL-R subjects differed significantly from the control subjectson the IKDC (P < 0.01), as well as on the KOOSpain (P < 0.05),

KOOSsymptoms (P < 0.01), KOOSsport (P < 0.01), and KOOSKQoL

(P < 0.01). The associated effects sizes were all large. There wasno statistically significant difference between the ACL-R subjectsand the control subjects on the KOOSADL (P > 0.05). These resultsare presented in Table 1.

3.2. Peak hip and knee joint kinematics

No between group differences were noted for peak hip jointadduction–abduction (P = 0.09), peak hip joint flexion–extension(P = 0.06) or peak hip joint internal–external rotation (P = 0.06).The ACL-R subjects exhibited a significantly less peak flexed posi-tion of the knee joint (P = 0.01). The associated effect size waslarge. No between group difference was noted for peak knee jointadduction–abduction (P = 0.05) or peak knee joint internal–exter-nal rotation (P = 0.96). The peak hip and knee joint kinematic pro-files are detailed in Table 2.

3.3. Time-averaged hip and knee joint kinematics

The hip joint flexion–extension kinematic profile differed signif-icantly (P < 0.05) between the ACL-R and control subjects, suchthat the ACL-R subjects exhibited a less flexed position of the hipjoint during the time period from 18 to 58 ms post-IC. The hip jointinternal–external kinematic profile differed significantly (P < 0.05),such that the ACL-R subjects exhibited a more internally rotatedposition of the hip joint during the time period from 108 to128 ms post-IC. The knee joint adduction–abduction kinematicprofile differed significantly (P < 0.05) between the ACL-R and con-trol subjects, such that the ACL-R subjects exhibited a more ab-ducted position of the knee joint during the time period from 86to 142 ms post-IC and from 160 to 200 ms post-IC. The knee jointflexion–extension kinematic profile differed significantly(P < 0.05) between the ACL-R and control subjects, such that theACL-R subjects exhibited a less flexed position of the knee jointduring the time period from 30 to 200 ms post-IC. The differencestime-averaged profiles are presented in Figs. 2–5.

4. Discussion

The primary aim of the present study was to investigate hip andknee joint kinematic profiles of ACL-R female athletes during per-formance of a diagonal jump landing. The main, hypothesis wasthat female athletes who have previously undergone ACL recon-struction surgery but who have since returned to full sporting par-ticipation (same sporting level as that participated in prior toinjury) would display altered hip and knee joint kinematic profiles,when compared to a non-injured sex and activity matched controlgroup. The findings of the present study support the main hypoth-esis, with the ACL-R group exhibiting altered sagittal plane andtransverse plane hip joint kinematic profiles, as well as altered sag-ittal plane and frontal plane knee joint kinematic profiles.

4.1. Subjective knee questionnaires

The IKDC is a valid and reliable knee specific measurement ofsymptoms, function and sports activity that is appropriated for pa-tients with a wide variety of knee problems, and has previouslybeen validated for use with an ACL reconstruction population (Ris-berg et al., 1999). In the present study a significant difference(P < 0.01) was observed for the IKDC scores of the ACL-R(81.43 ± 11.76) and control (99.06 ± 3.73) groups. The differencebetween the mean scores of both groups was >9 points whichhas been reported to be the threshold for identifying a clinically

Table 1IKDC and KOOS subscale results.

IKDC KOOSpain KOOSsymptoms KOOSADL KOOSsport KOOSQOL

Control 99.06 ± 3.73 99.81 ± 0.75 98.37 ± 2.62 99.81 ± 0.75 99.37 ± 2.50 99.25 ± 2.04ACL-R 81.43 ± 11.76* 91.00 ± 11.47* 83.84 ± 8.34* 97.84 ± 4.56 79.61 ± 15.47* 71.76 ± 15.74*

Effect size (eta squared) 0.54 (large) 0.25 (large) 0.61 (large) 0.09 (small) 0.48 (large) 0.64 (large)

Values are presented as mean ± SD.* Significantly different from control participants.

Table 2Peak hip and knee joint angular displacements (degrees).

ACL-R Control P Value Effect Size (eta squared)

Hip adduction–abduction angle (degrees) �5.04 ± 6.03 �9.04 ± 5.87 0.09 0.10 (medium)Hip flexion–extension angle (degrees) 29.77 ± 6.84 34.62 ± 6.45 0.06 0.12 (medium)Hip internal–external rotation angle (degrees) 3.20 ± 8.16 �1.52 ± 4.27 0.06 0.13 (medium)Knee adduction–abduction angle (degrees) �3.63 ± 3.92 �1.11 ± 2.76 0.05 0.13 (medium)Knee flexion–extension angle (degrees) 42.66 ± 9.29 51.40 ± 7.62 0.01* 0.22 (large)Knee internal–external rotation angle (degrees) 12.13 ± 6.04 12.02 ± 6.62 0.96 0.00 (small)

Values are presented as mean ± SD.Hip adduction–abduction; adduction is positive, abduction is negative.Hip flexion–extension; flexion is positive, extension is negative.Hip internal–external rotation, internal rotation is positive, external rotation is negative.Knee adduction–abduction; adduction is positive, abduction is negative.Knee flexion–extension; flexion is positive, extension is negative.Knee internal–external rotation; internal rotation is positive, external rotation is negative.* Significantly different from control participants.

Fig. 2. Hip joint flexion–extension angle. Flexion is positive; shaded area = area of statistical significance. 0 = initial contact with the force-plate. Values are mean SD.

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meaningful effect (Irrgang et al., 2001) while the associated effectsize (0.54) was large.

The KOOS questionnaire was designed to evaluate short termand long term symptoms and function in patients with a varietyof knee injuries that could possibly result in osteoarthritis (Rooset al., 1998) and has previously been validated for use with an

ACL reconstruction population (Roos et al., 1998). The KOOS hasseparate scores for the different aspects of the questionnaire,which are; pain, symptoms, activities of daily living, sport andrecreation function, and knee related quality of life. In thepresent study a significant difference (P < 0.01) between theACL-R and control groups was observed on four of the KOOS

Fig. 3. Hip joint internal–external rotation angle. Internal rotation is positive; shaded area = area of statistical significance. 0 = initial contact with the force-plate. Values aremean SD.

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subscales: (KOOSpain ACL-R = 91.00 ± 11.47, control = 99.81 ± 0.75;KOOSsymptoms ACL-R = 83.84 ± 8.34, control = 98.37 ± 2.62;KOOSsport ACL-R = 79.61 ± 15.47, control = 99.37 ± 2.50; KOOSKQoL

ACL-R = 71.76 ± 15.74, control = 99.25 ± 2.04). The associated effectsizes were all large, indicating the clinical meaningfulness of thedifference between the group means. No significant between-group difference (P > 0.05) was observed on the KOOS ADL subscale.The observation of no significant between-group difference for theKOOS ADL is not an unexpected result as Hambly and Griva (2010)reported that the items for the KOOSADL were neither viewed asbeing particularly important by participants, nor were they fre-quently experienced. Furthermore, the questions in the KOOSADL

involve low stress tasks such as taking off socks and climbingstairs, and thus these specific aspects of daily life would not be ex-pected to pose any difficulty for the female athletes in the presentstudy. The results of the present study show that although ACLreconstruction may allow for a return to sporting participation,the injury continues to affect patients in several different aspectsof their life, for a long time post-reconstruction. However, consid-eration must be given to the use of the KOOS in the present study,as recent research suggests that its application to an ACL popula-tion may not be warranted (Comins et al., 2008).

4.2. Hip and knee joint kinematics

Following IC the ACL-R group where characterized by a de-creased time-averaged hip joint flexed position during the timeperiod from 24 to 58 ms post-IC (P < 0.05). Previous research hasestablished that women athletes exhibit less hip joint flexion uponlanding from jumps when compared to male athletes (Griffin et al.,2006). Thus, the results of the present study support the findings of

Griffin et al. (2006) and suggest that this abnormal hip joint kine-matic profile observed in female athletes may be compounded byACL reconstruction surgery. The exact consequence of this alteredkinematic profile and whether this profile was present prior to in-jury cannot be elucidated from the present study but is worthy offuture investigation.

Following IC the ACL-R group where characterized by an in-creased time-averaged hip joint internal rotation position duringthe time period from 108 to 128 ms post-IC (P < 0.05). Further-more, during this time period the ACL-R group were in a positionof hip joint internal rotation which contrasts with the externalrotation position observed in the control group. It is well estab-lished that hip joint internal rotation is a contributing factor to dy-namic valgus collapse at the knee joint (Hewett et al., 2005;Schmitz et al., 2009; Krosshaug et al., 2007; Paterno et al., 2010).Thus, the observed increased internally rotated position of thehip joint in the ACL-R group during the time period from 108 to128 ms post-IC could influence knee joint frontal plane movementand thus valgus collapse at the knee joint.

At IC the ACL-R group displayed an abducted position of theknee joint compared to an adducted position observed in the con-trol group. From approximately 40 ms after IC the ACL-R group in-creased this abducted position for a period or approximately70 ms, whilst remaining in an abducted knee position throughoutthe entire 200 ms time period following IC. This contrasts withthe control group who remained in an adducted knee joint positionthroughout the entire 200 ms post-IC. During the time periodsfrom 88 to 140 ms post-IC and from 164 to 200 ms post-IC the dif-ference in time-averaged knee joint frontal plane kinematic pro-files between the groups were significant (P < 0.05), with theACL-R exhibiting a more abducted knee joint position. In a dynamic

Fig. 4. Knee joint adduction–abduction angle. Adduction is positive; shaded area = area of statistical significance. 0 = initial contact with the force-plate. Values are mean SD.

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simulation model Chaudhari and Andriacchi (2006) have shownthat an increased abducted position of the knee joint decreasesthe threshold for ACL injury. An increased abducted knee joint(as a result of multi-planar aberrant hip and knee joint kinematics)position during sporting manoeuvres is well established as a keycomponent in the valgus collapse injury mechanism for non-con-tact ACL injury (Hewett et al., 2005). Furthermore, in a recentlypublished study Paterno et al. (2010) have shown that an increasein knee joint frontal plane movement is a predictive factor of 2ndACL injury following primary ACL reconstruction and return-to-play in female athletes. Thus, the observation of the increased fron-tal plane movement in the ACL-R group in the present study is inline with the findings of Paterno et al. (2010).

In the present study, the ACL-R group exhibited a decreasedtime-average knee joint flexed position during the time periodfrom 30 to 200 ms post-IC (P < 0.05). The ACL-R group also dis-played a decreased peak knee joint flexed position following ICwhen compared to the control group (42.66� ± 9.29� vs51.40� ± 7.62� respectively; P = 0.01). Altered knee joint sagittalplane angular displacement has been implicated as a componentin the ACL injury mechanism (Markolf et al., 1995; Pandy and Shel-burne, 1997; Li et al., 1999), by increasing the potential for anteriortibial displacement. Thus, the results of the present study indicatethe potential role for a sagittal plane knee joint deficit as a contrib-uting factor to future knee joint injury in ACL reconstructedathletes.

In the present study the timing of specific kinematic differencesbetween the ACL-R and control group are interesting and comparefavourably with a recently published study by Koga et al. (2010).The study by Koga et al. (2010) suggests that ACL injury occurs

approximately 40 ms post-IC, with the injury mechanism beingcharacterized by a low knee flexion angle and a sudden increasein knee joint abduction within a 40 ms time period following IC.The results of our study indicated that the ACL-R athletes remainin a less knee joint flexed position from 30 to 200 ms post-IC. Alsoof particular note was that the ACL-R group started to move to-wards a position of increased knee joint abduction at approxi-mately 40 ms post-IC, when compared to the control group whoremained in an adducted position of the knee joint during the200 ms post-IC. Furthermore, the ACL-R athletes also started to de-crease their position of hip joint external rotation at approximately30 ms post-IC reaching a position of internal rotation at approxi-mately 90 ms post-IC. We believe that these noted aberrant kine-matic profiles in the ACL-R group contribute to a dynamic valguscollapse of the knee joint and provide an important insight to po-tential knee joint injury mechanisms following return to sport afterACL reconstruction surgery.

The present study does have the limitation that we were unableto account for and track different forms of rehabilitation utilizedafter the surgery. We would recommend that future studies shouldtake into account rehabilitation protocols and report on these. Fur-thermore, in the present study we did not measure quadricepsstrength which may influence hip and knee joint kinematics duringthe performance of jump landings in subjects following ACL recon-struction (Gokeler et al., 2012). A further limitation of the presentstudy was the fact that it was cross-sectional in design. Two pub-lished studies suggests that lower limb kinematic and kineticchanges during puberty may result in an increased risk of kneejoint injury in female athletes when compared to age matchedmale athletes (Ford et al., 2010a,b). Thus, it is possible that the

Fig. 5. Knee joint flexion–extension angle. Flexion is positive; shaded area = area of statistical significance. 0 = initial contact with the force-plate. Values are mean SD.

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observed aberrant lower limb kinematic profiles in the ACL-Rgroup in the present study were present even before the incitingevent.

4.3. Conclusion and practical application

Future knee joint injury or re-rupture are of particular concernto sports medicine clinicians following ACL reconstruction. Alteredknee joint kinematics, have been implicated in the mechanism ofinjury for 1st time ACL rupture (Hewett et al., 2005). However,the extent to which knee joint kinematic profiles are restored fol-lowing ACL surgery remains largely unknown. The result of thepresent study indicate that even following ACL reconstructionand full return to sporting participation the female athletes inthe present study still exhibited altered hip and knee joint kine-matic profiles. The altered kinematic profiles observed could con-tribute to dynamic knee joint valgus collapse and thus increasethe risk of future knee joint injury and re-rupture. We advocatethe use of specific neuromuscular training incorporating staticand dynamic postural stability drills, lower limb strengthening,plyometrics, and speed and agility drills following ACL reconstruc-tion to enhance knee joint sensorimotor control in female ACL-Rathletes. Future studies are now required to determine if neuro-muscular training can reduce the incidence of knee joint injuryand re-rupture following ACL reconstruction in female athletes.

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Eamonn Delahunt graduated with a 1st Class HonoursDegree from the UCD School of Physiotherapy in 2003.Upon graduation Eamonn was the recipient of a pres-tigious IRCSET post-graduate research scholarship. Hewas awarded his PhD from the UCD School of Physio-therapy and Performance Science in 2006. Eamonn hasbeen the recipient of numerous research bursaries forhis research on chronic ankle instability and has pub-lished on this topic in all the leading Sports Medicine/Science journals. He currently works as a college lec-turer in the UCD School of Public Health, Physiotherapyand Population Science, and acts as the Programme Co-ordinator for the B.Sc. Health and Performance Science

Degree Programme. Eamonn also has extensive clinical experience having previ-ously worked as a Chartered Physiotherapist in ExWell Medical. Eamonn also cur-rently works as the Academic Mentor to the UCD Elite Athlete Academy.

Anna Prendiville was a final year under-graduate stu-dent at the time of completion of the current paper. Shegraduated in September 2011, obtaining a 2H1 degreeclassification in the B.Sc. Health & Performance Scienceprogramme, University College Dublin. Anna has pre-viously published papers relating to lower limb kine-matics following anterior cruciate ligament surgery.Anna was part of a research group who were the reci-pient of the award for best poster presentation at the8th Annual Scientific Conference of the FSEM, RCPI &RCSI.

Lauren Sweeney was a final year under-graduate stu-dent at the time of completion of the current paper. Shegraduated in September 2011, obtaining a B.Sc. Health &Performance Science from University College Dublin.Lauren has previously published papers relating tolower limb kinematics following anterior cruciate liga-ment surgery. She was part of a research group whowere the recipient of the award for best poster presen-tation at the 8th Annual Scientific Conference of theFSEM, RCPI & RCSI.

606 E. Delahunt et al. / Journal of Electromyography and Kinesiology 22 (2012) 598–606

Mark Chawke graduated from University College Dub-lin B.Sc. Health & Performance Science programme in2011. At the time of completion of the current researchproject he was an under-graduate student. Since grad-uation he has continued his involvement in lower limbbiomechanical research with a particular emphasis onanterior cruciate ligament injury epidemiology andprevention. Mark was part of a research group whowere the recipient of the award for best poster presen-tation at the 8th Annual Scientific Conference of theFSEM, RCPI & RCSI.

Judy Kelleher was a final year under-graduate studentat the time of completion of the current paper. Shegraduated in September 2011, obtaining a 2H1 degreeclassification in the B.Sc. Health & Performance Scienceprogramme, University College Dublin. At the time ofcompletion of the current research project she was anunder-graduate student. Judy was part of a researchgroup who were the recipient of the award for bestposter presentation at the 8th Annual Scientific Con-ference of the FSEM, RCPI & RCSI.

Matt Patterson attained a B.Sc. in Kinesiology from theUniversity of Waterloo in 2003. After graduation Mattspent several years in industry, designing motion anal-ysis tools based on inertial sensor technology. Thistechnology was used by top professional sports teams inNorth America. In 2009, based on his in-depth knowl-edge of human movement and signal processing Mattwas the recipient of a prestigious SFI-CLARITY graduateresearch scholarship to work on a Ph.D. at UniversityCollege Dublin. He currently is in the final year of hisPhD.

Katie Murphy was a final year under-graduate studentat the time of completion of the current paper. Shegraduated in September 2011, obtaining a 2H1 degreeclassification in the B.Sc. Health & Performance Scienceprogramme, University College Dublin. At the time ofcompletion of the current research project she was anunder-graduate student. Katie was part of a researchgroup who were the recipient of the award for bestposter presentation at the 8th Annual Scientific Con-ference of the FSEM, RCPI & RCSI. Katie is currentenrolled as an under-graduate physiotherapy student atUniversity College Dublin.