Elsevier

Journal of Biomechanics

Volume 34, Issue 9, September 2001, Pages 1107-1115
Journal of Biomechanics

Dynamic and static control of the human knee joint in abduction–adduction

https://doi.org/10.1016/S0021-9290(01)00080-XGet rights and content

Abstract

It is unclear whether humans can voluntarily control dynamic and static properties in knee abduction–adduction, which may be important in performing functional tasks and preventing injuries, whether the main load is about the abduction axis or not. A joint-driving device was used to perturb the knee in abduction–adduction at full knee extension under both passive (muscle relaxed) and active (muscle contracted in abduction or adduction) conditions. Dynamic control properties in knee abduction–adduction were characterized by joint stiffness, viscosity, and limb inertia, and quasi-static knee torque-angle relationship was characterized by knee abduction–adduction laxity and quasi-static stiffness (at a 20 N m moment). It was found that the subjects were capable of generating net abduction and adduction moment through differential co-contraction of muscles crossing the medial and lateral sides of the knee, which helped to reduce the abduction–adduction joint laxity (p⩽0.01) and increase stiffness (p<0.027) and viscous damping. Knee abduction laxity was significantly lower than adduction laxity (p=0.043) and the quasi-static abduction stiffness was significantly higher than adduction stiffness (p<0.001). The knee joint showed significantly higher stiffness and viscosity in abduction–adduction than their counterparts in knee flexion-extension at comparable levels of joint torque (p<0.05). Similar to dynamic flexion-extension properties, the system damping ratio remained constant over different levels of contraction, indicating simplified control tasks for the central nervous system; while the natural undamped frequency increased considerably with abduction–adduction muscle contraction, presumably making the knee a quicker system during strenuous tasks involving strong muscle contraction.

Introduction

The human knee is a complex joint with considerably different properties in the sagittal, frontal, and transverse planes. The knee is subject to substantial abduction–adduction moment during functional activities and excessive load in abduction–adduction is closely related to knee injuries (Andriacchi et al., 1980; Kowalk et al., 1993; Schipplein and Andriacchi, 1991; Pope et al., 1979; Buchanan and Lloyd, 1997; Lloyd and Buchanan, 1996; Yasuda et al., 1993). However, it is not very clear whether humans can voluntarily control dynamic and static properties in knee abduction and adduction, which may be important in performing functional tasks and preventing injuries, whether the major load is in the frontal plane or not.

Compared with knee flexion-extension properties (Franken et al., 1993; Stein et al., 1996; Zhang et al., 1998), much less work has been done on knee abduction–adduction characteristics. Several studies were done on static properties of knee abduction–adduction, including laxity and quasi-static stiffness (Goldfuss et al., 1973; Markolf et al., 1978; Pope et al., 1979; Mills and Hull, 1991). Some reported knee abduction–adduction laxity reduced significantly when the quadriceps and hamstrings were pretensed (Goldfuss et al., 1973) or when knee flexion-extension torque was generated (Olmstead et al., 1986). Others found that contraction of the sartorius and vastus medialis increased the valgus stiffness substantially (Pope et al., 1979). No voluntary torque specifically in knee abduction or adduction was used and dynamic control of knee abduction–adduction with muscles generating knee abduction–adduction moment was not evaluated in the above studies. Lack of information on dynamic control of knee abduction–adduction is partly due to the difficulties involved in manipulating the knee dynamically in abduction–adduction, and partly due to the difficulty of separating hip rotation from knee abduction–adduction when the knee is flexed. Even at full knee extension where the hip rotation is not likely to contribute to knee abduction–adduction, it is unclear whether humans can control knee abduction–adduction within the limited abduction–adduction range of motion (Zhang et al., 2001).

The purpose of this study was to investigate in vivo dynamic and static control of the knee in abduction–adduction under both passive (muscle relaxed) and active (muscle contracted in abduction or adduction) conditions. The following hypotheses were tested: (1) humans could control knee dynamic properties (joint stiffness and viscous damping) in abduction and adduction; (2) dynamic properties (joint stiffness and viscous damping) in knee abduction–adduction were different from their counterparts in knee flexion-extension; (3) humans could control knee static properties (joint laxity and quasi-static stiffness) in abduction and adduction;

(4) static properties (laxity and quasi-static stiffness) at the extreme knee abduction were different from that at the extreme knee adduction. Study of these properties will help us better understand the neuromuscular control of the knee in 3-D space, and evaluate knee injuries, surgical outcome, and rehabilitation progress.

Section snippets

Methods

Nine male subjects with no prior history of lower-limb injury participated in the study and gave informed consent (Table 1). The subject sat upright in a joint-driving device with the hip at 85° flexion (Fig. 1). The knee was placed at full extension to minimize the contribution of hip rotation to knee abduction. The tibia was at the neutral axial rotation and abduction. The knee abduction–adduction axis was chosen as intersecting the transepicondylar line at the midpoint between the

Dynamic control in knee abduction–adduction (Hypothesis 1)

Joint stiffness in knee abduction–adduction increased with abduction–adduction muscle contraction significantly between every two consecutive muscle contraction levels with an increment of 3 N m (p<0.027) (Fig. 3). It increased from 285.3±48.6 N m/rad at the relaxed state to 435.2±74.0 and 452.2±83.4 N m/rad at 18 N m abductor and adductor muscle torques, respectively. Similarly, joint viscosity in knee abduction–adduction also increased with the level of muscle contraction, from 3.6±1.4 N m s/rad at the

Discussion

Although the human knee sustains substantial abduction–adduction load during various functional activities, there is lack of information on the dynamic control of knee abduction–adduction. The dynamic and quasi-static control in knee abduction–adduction were investigated in vivo in this study under both passive (muscle relaxed) and active (muscle contracted in abduction or adduction) conditions and compared to their counterparts in knee flexion-extension. It was shown that under controlled

Acknowledgements

The authors gratefully acknowledge the supports of the NIH (LZ), Whitaker Foundation (LZ), and Falk Medical Research Trust (LZ).

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