Gait characteristics of patients with knee osteoarthritis
Introduction
Osteoarthritis (OA) is the most prevalent form of arthritis in the elderly. This disease is particularly disabling when the knees are affected. It is estimated that 9% of men and 18% of women over age 65 have knee OA (Davis et al., 1991). Individuals with knee OA experience pain, stiffness, and decreased range of motion of the joints. These symptoms significantly limit an individual's ability to rise from a chair, stand comfortably, walk, or climb stairs. Ultimately, these limitations lead to a loss of functional independence.
The mechanics of walking on a level surface are well understood and characterized (Bresler and Frankel, 1950; Perry, 1992). Several studies have also analyzed the mechanics of stair walking. Kinematic and kinetic data of the lower limb in the sagittal plane during stair ascent and descent have been described in the sagittal plane (Andriacchi et al., 1980; McFadyen and Winter, 1988), and the frontal plane (Andriacchi et al., 1980; Kowalk et al., 1996; Yu et al., 1996). However, all of these studies have been conducted on able-bodied subjects. Few studies have quantified the gait changes associated with knee OA. One study has shown a reduction in sagittal plane knee motion (Stauffer et al., 1997). Three studies have shown a relationship between the knee adduction moment, OA disease severity and knee alignment (Schnitzer et al., 1993; Weidenhielm et al., 1994; Sharma et al., 1998). All of these studies were conducted on a level surface.
A greater understanding of gait will be useful for quantifying the pathomechanics of patients with knee OA. These patients experience pain and thus may compensate to minimize joint loading and resultant pain. Therefore, the purpose of this study was to analyze the gait characteristics of subjects with knee OA. The hypothesis tested was that the knee kinematics and kinetics would be significantly lower than normal in this population.
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Methods
This study was performed on 139 adults diagnosed with knee OA. There were 47 males and 92 females in the study population. The subjects ranged in age from 30 to 82, and had a mean age of 57 years (±12.5). Their mean weight was 85 kg (±17) and their mean height was 167 cm (±9.7). Subjects were recruited on a volunteer basis to participate in the study. Enrollment was sought by advertisements in local newspapers. Potential subjects were initially contacted by telephone. Those individuals who seemed
Results
The subjects with OA walked slower than the normal subjects (Table 2). These differences in walking velocity were statistically significant (p<0.01).
The knee kinematic patterns were different for each of the walking conditions (Fig. 1). During level walking there was an initial loading response (knee flexion) with the greatest knee flexion during swing. During stair ascent the knee started in a flexed position and extended throughout the entire stance phase. Conversely, during the stance phase
Discussion
Walking is a common functional activity of daily living. This study provides meaningful information on gait adaptations used by patients with knee OA. These adaptations provide pain relief from the dynamic joint loading encountered during gait. Subjects with OA exhibited significantly lower knee extensor moments during gait. The contact forces in the knee joint are proportional to the net external reaction moment. A large internal moment, needed to balance a large external moment, will produce
Acknowledgements
Funding from American Home Products supported this study. The authors thank Diana Hansen and Ann Walker for their assistance with data collection and reduction, and Barbara Iverson-Literski for her careful manuscript preparation.
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