Balance Control and Inter-Joint Coordination in Patients with Degenerative Knee Osteoarthritis During Obstacle-Crossing
Date Issued
2009
Date
2009
Author(s)
Wang, Ting-Ming
Abstract
Osteoarthritis (OA), defined by degradation of the articular cartilage and an increase in subchondral bone density, is a common joint disorder in the elderly. Knee OA has also been associated with falls in the elderly. Knee OA has been reported to affect the performance of ambulation, including level walking and obstacle-crossing. An increased risk of falling in patients with knee OA during obstacle-crossing, as opposed to unobstructed level walking, may be explained by the difference in the control of the body’s center of mass (COM) with respect to the center of pressure (COP) while trying to ensure sufficient foot clearance. Knowledge of the control of the body’s dynamic stability in patients with knee OA is helpful for the management of these patients and for the evaluation of treatment outcomes. In the present study, young, older and knee osteoarthritic subjects were recruited to investigate the influence of aging and aging-related disease on the balance control and inter-joint coordination of obstacle-crossing using motion analysis techniques. In young subject, it was found that vertical components of the COM motion, including position, velocity and acceleration, were all modulated to successfully cross obstacles of different height and that these modulations were different between the leading and trailing limbs. Since the acceleration of the COM is directly related to the forces applied to the COM, the increase in the magnitude of the M/L acceleration of the COM with increasing obstacle height suggests that increased forces from muscle contractions are required to ensure the control of the smooth transition of the COM position between single and double stance phase. If the M/L stability is compromised, due to muscle weakness or degradation of coordination, falls may occur. Whole body control through adjustments of the A/P acceleration of the COM to reduce A/P COM-COP distances was required for the necessary stability in the sagittal plane when crossing obstacles of increased height. For the elderly, at this critical time during obstacle-crossing the older group used smaller medial COM-COP inclination angles to cross the obstacle successfully without falling sideways, suggesting that the neuromusculoskeletal system may have more room to control the swing foot with sufficient foot clearance. Decreased inclination angles with increasing obstacle height suggest that the subjects tended to keep their COM position close to the COP position to increase the body’s stability. For the patients with knee OA, normal COM positions and velocities were found at key instances during the walking cycle but with significant changes in COM accelerations. This more jerky motion of the body’s COM may be a result of reduced ability associated with knee OA in the control of the motion of the COM. For better control of the COM in the A/P direction during the more challenging latter half of SLS, adjustments to the A/P acceleration of the COM throughout the complete gait cycle were needed. Diminished A/P COM–COP separation was a conservative strategy for patients with knee OA in order to maintain body stability with reduced joint loadings. In the frontal plane, this was achieved by increasing the acceleration of the body’s COM towards the stance leg. Strengthenging of the muscles of the lower extremities, as well as training of the control of the COM through a dynamic balance training program, are equally important for the dynamic stability of patients with knee OA. When comparing body’s center of mass motion during unobstructed with those during obstructed gait in patients with knee osteoarthritis, modulation of inclination angle and angular velocities were necessary when facing more challenging tasks such as obstacle-crossing, particularly so in patients with knee OA. While less stable COM control was found around the end stage of double stance phase during obstacle-crossing when compared to level walking, patients with knee OA successfully acquired strategies in the sagittal plane to maintain close-to-normal stable COM control with normal toe clearance during both level walking and obstacle-crossing. They achieved stable transitions from SLS to DLS through a reduced anterior inclination angle and from DLS to SLS through an increased anterior angular velocity. It is suggested that assessment of the ability to control dynamic stability in patients with knee OA should consider both the positions and velocities of the COM and the COP. For the inter-joint coordination, despite significant changes of the joint kinematics knee OA did not change significantly the way the motions of the lower limb joints are coordinated during obstacle-crossing. It appears that the OA group had adopted a particular biomechanical strategy among all possible strategies that can accommodate the OA-induced changes in the knee mechanics using unaltered inter-joint coordination control. This enabled the OA subjects to accommodate reliably the mechanical demands related to bilateral knee OA in the sagittal plane during obstacle-crossing. Maintaining normal and reliable inter-joint coordination could be considered as an outcome of therapeutic intervention, and the patterns and variability of inter-joint coordination can be used to evaluate treatment effects.
Subjects
Osteoarthritis of the knee
walking, obstacle-crossing
COM
COP
dynamic stability
inter-joint coordination.
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
index.html
Size
23.49 KB
Format
HTML
Checksum
(MD5):a71ed60a4ada2936c8466c5c70b61980