A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait
Introduction
The anterior cruciate ligament (ACL) is commonly injured and patients with ACL tears have been reported to demonstrate various alterations in walking [1], [2], [3]. Berchuck et al. [3] popularized the concept of quadriceps-avoidance, an external extension moment at the knee in stance in the ACL-deficient patients, as an attempt to decrease anterior shear forces on the tibia. However, other investigators have been unable to reproduce the phenomenon of quadriceps avoidance (an external knee extension moment) in ACL-deficient patients.
Kadaba et al. [4] reported a flexed knee pattern combined with external knee flexion moments, rather than a quadriceps avoidance pattern in unreconstructed ACL-deficient patients. Patients in the post-operative period after ACL reconstruction with a patellar tendon autograft from the extensor mechanism, where it would be expected that quadriceps avoidance would be easily observable, have not demonstrated this adaptation [5]. Snyder-Mackler et al. [6] reported kinematic alterations consistent with a co-contraction strategy of the quadriceps and hamstrings in the early postoperative phase after ACL reconstruction. Beard et al. [7] reported an increase in the duration of hamstring activity with similar quadriceps activity duration while exhibiting external flexion moments at the knee in ACL-deficient subjects with respect to controls.
Our first purpose was to corroborate previous studies in this area regarding the phenomenon of an increased internal flexion moment during stance (quadriceps avoidance) in a population of patients with ACL tears. This was done using a video-based motion analysis system and surface electromyography (EMG). Our second purpose was to determine if there are any other mechanisms, besides decreased quadriceps muscle activity, that might account for any observed internal flexion moment or decreased internal extension moment in stance.
Section snippets
Subjects
A complete medical history was obtained from each patient. All patients were interviewed and a comprehensive lower extremity physical examination (which included ligament testing, range of motion, manual muscle testing and observation of gait) was conducted by the primary author using a modified Cincinnati Knee Rating System [8].
The 18 subjects of this study had a unilateral ACL-deficiency. All patients had a positive Lachman’s sign and a grade two or three pivot shift maneuver (Table 1). In
Results
Typical clinical gait analysis kinematic plots (ensemble averaged for all subjects) are shown in Fig. 1 (stride side) and Fig. 2 [non-stride side (termed opposite side in this paper)]. Saggital view stride side moment and power plots (ensemble averaged for all subjects) are shown in Fig. 3. Except for the stride and opposite side knee plots and the opposite side ankle plots, the ensemble averaged kinematic and kinetic plots fall within the ±1 S.D. plots of the normal subjects.
None of the
Discussion
We did not find a significantly different knee kinematic or kinetic pattern in early stance or a decreased duration of quadriceps activity in any ACL-deficient subject. We expected to find quadriceps avoidance in at least some of our subjects. Berchuck et al. [3] reported that 75% of their patients with ACL tears had a flexed knee gait and absence of an extension moment. Noyes et al. [8] found quadriceps avoidance in 50% of patients with ACL-deficiency and varus alignment. Birac et al. [13] in
Acknowledgements
Funding for this study was made possible through a grant from the Jewish Hospital Foundation, Louisville, KY. Additionally, the authors wish to thank Dr Terry Horn, Dr Murali Kadaba and Dr Peter Quesada for their review and editorial comments related to this manuscript.
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