Fitness Research update
Anterior knee shear and rotation during exercise in acl injury

Fitness Research is a partnership between Australian Fitness Network, the University of the Sunshine Coast and the Australian Institute of Fitness. Colleagues at USC recently published the following study that aligns with the partnership's mission of improving the health of Australians through an improved body of fitness knowledge.

Research paper: Tibial displacement and rotation during seated knee extension and wall squatting: A comparative study of tibiofemoral kinematics between chronic unilateral anterior cruciate ligament deficient and healthy knees.

Research team: Dr Sue Keays, Dr Mark Sayers, Mr Daniel Mellifont, Dr Carolyn Richardson; University of the Sunshine Coast

Published: The Knee, 2012 Jul 31 [epub ahead of print]

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Introduction: Anterior cruciate ligament (ACL) injuries are increasingly common during sport and exercise. Clinicians strive to provide optimal rehabilitation to individuals with ACL-deficiency (i.e. post-ACL rupture) or post-ACL reconstruction. Following ACL rupture, the knee becomes unstable with alterations in joint kinematics, including anterior tibial displacement (ATD; sometimes referred to as ‘anterior shear’), and internal tibial rotation.

Important long-standing research has established that quadriceps exercises may be unsafe as they have the potential to disturb graft integrity by increasing ATD. However, studies in the 1980s and 1990s found that avoiding quadriceps exercises post-surgery led to major problems in the restoration of function. Subsequently, the focus on quadriceps rehabilitation has returned and the critical question remains regarding which quadriceps exercises are safe and at what stage during rehabilitation they can be commenced. Closed kinetic chain (CKC) exercises became favoured over open chain because the accompanying joint compression was considered to limit ATD. However, controversy regarding the safety of open versus closed chain quadriceps exercises with regard to ATD and rotation continues. A summary of the evidence is provided in Table 1.

Figure 1. Open chain seated extension and closed chain single leg squat exercises were assessed in ACL-deficient and healthy participants.

Our study aimed to compare ATD and tibial rotation during two commonly prescribed exercises, namely: open kinetic chain (OKC) seated knee extension and closed kinetic chain (CKC) single leg wall squatting in ACL-deficient and healthy knees.

Methods: 3D motion analysis (Qualisys 3D-Motion Analysis System tracking 17 infrared markers) of the knee during seated knee extension with 3kg weight and a unilateral wall squat (see Figure 1) was performed with eight ACL deficient patients and eight healthy subjects matched for age, gender and sports history. We developed a model to measure joint kinematics through 70° of knee flexion and extension. ANOVA (analysis of variance) and paired t-tests compared relative ATD and tibial rotation between exercises and groups at 10° increments of flexion and extension.

Results: We found significantly less control of knee shear (i.e. increased ATD) in the wall squat compared to the seated extension for both healthy and ACL-deficient knees (p=.049). Participants with ACL-deficiency also showed abnormal internal rotation of the tibia with both exercises (i.e. the tibia was significantly more internally rotated (p=.003) in ACL-deficient knees, irrespective of the exercise). The most likely reason for the absence of differences in ATD between injured and healthy knees was that some ACL-deficient knees (copers) behaved more like normal knees, showing less ATD (Figure 2a) while others (non-copers) (2b) showed greater ATD. The latter may be representative of ineffective movement adaptation and coping.

Take home messages: Do not assume that all closed chain knee exercises are safe. Seek advice from the treating clinician (e.g. physiotherapist) when prescribing exercises for people with ACL injuries or surgery. Do not use wall squats or loaded open chain knee extension exercises for these clients unless you are certain they can maintain knee control (including knee shear/ATD and tibial rotation). Exercises need to be individually assessed and carefully prescribed. It remains essential to focus on the individual’s functional ability and control when prescribing and performing exercise.

Summary: Exercises that promote faulty knee movement (e.g. ATD or tibial rotation) should be discouraged, especially early post-ACL reconstruction. The early use of open chain knee extension resistance exercises in ACL rehabilitation is associated with increased joint laxity. In recent years, many clinicians have favoured the use of various closed chain exercises regardless of their effect on ATD and tibial rotation. However, this study suggests that wall squats may result in similar changes in tibial rotation and more ATD than open chain knee extension.

Figure 2: The amount of anterior tibial displacement during two single leg wall squats and two seated extensions in two ACLD subjects. Figure 2a is representative of some ACLD participants, possibly with more dynamically stable knees, and shows a similar profile to participants with healthy knees. Here the tibia moves posteriorly from 0°-70° of knee flexion. Figure 2b is representative of a possibly less dynamically stable group of ACLD participants. Here the tibia remains more anteriorly displaced throughout range more so in the CKC wall squat than the OKC seated extension.

Table 1:  Literature Findings using Direct Measures to Assess Tibial Displacement and Rotation in ACL-deficient and Intact Knees



Van der Velde et al 2009

Increased internal rotation and ATD in ACLD knees following transaction.

Mannel et al 2004

Increased anterior and medial translation following ACL transaction.

Kanamori et al  2000

Increased ATD occurred in the ACLD compared to the intact knee on application on a 10Nm force.

Carpenter et al 2009

When moving into extension ACLR knees showed  3.5° more internal tibial rotation than contralateral knees.

Scarvell et al 2005

Tibiofemoral contact pattern more posterior indicating increased internal rotation of the tibia with flexion during a leg press.

Seon et al 2007

Single- bundle reconstructions showed increased sagital translation compared to double bundled and contralateral knees during static NWB at 30°, 60°, 90° and 120°.

Shefelbine et al 2006

Increased ATD from 45° to full extension comparing ACLD to uninjured knee during WB.

DeFrate et al 2006

Increased ATD and internal rotation at low flexion angles in ACLD compared to intact knees assessed during static lunging ranging from 0°-90°.

Jonsonn et al 1989

Increased anterior tibial displacements and increased internal rotation compared to intact knees from 30°-0°.

Georgoulis et al  2003

ACLD subjects internally rotated   during early swing phase of walking. ACL-reconstructed and healthy knees externally rotated.

Brandsson et al 2001

Increased internal rotation of tibia in ACLD knees during a step up.

Lysholm  and Messner 1995

Increased sagital  translation during isotonic exercises, cycling and walking downstairs .

Deneweth et al 2010

Increased external tibial rotation and ATD in reconstructed   compared to contralateral knees during single hop..

Beard et al 2001

Increased ATD post reconstruction compared to contralateral knees with walking.

Waite et al 2005[29]

Increased internal  tibial rotation and increased medial translation in ACLD compared to contralateral knees  but no difference in ATD during running and cutting.

Nagano  et al 2009[30]

Increased internal tibial rotation and knee adduction make plant and cutting risky in females.

Yack et al 1993[31]

ATD greater during active extension than squatting in ACLD but not in normal knees.

Jenkins et al 1997[32]

Greater ATD in open chain situation compared to leg press.