Reports of joint instability in knee osteoarthritis: Its prevalence and relationship to physical function
Article first published online: 8 DEC 2004
Copyright © 2004 by the American College of Rheumatology
Arthritis Care & Research
Volume 51, Issue 6, pages 941–946, 15 December 2004
How to Cite
Fitzgerald, G. K., Piva, S. R. and Irrgang, J. J. (2004), Reports of joint instability in knee osteoarthritis: Its prevalence and relationship to physical function. Arthritis & Rheumatism, 51: 941–946. doi: 10.1002/art.20825
- Issue published online: 8 DEC 2004
- Article first published online: 8 DEC 2004
- Manuscript Accepted: 20 JUN 2003
- Manuscript Received: 30 MAY 2003
- Western Pennsylvania Chapter of the Arthritis Foundation
- Physical function
To report the prevalence and relationship of self-reported knee instability to physical function in a sample of subjects with knee osteoarthritis (OA), and to discuss the implications of these observations for rehabilitation.
Subjects were 105 individuals (80 females) with knee OA who rated their knee instability severity on a 6-point numeric scale in response to the query “To what degree does giving way, buckling, or shifting of the knee affect your level of daily activity?” A principal component analysis was used to combine The Western Ontario and McMaster Universities pain, stiffness, and physical function subscale scores, and the Timed Get Up and Go Test score into a principal component score for physical function (PCPF). Other variables that could affect the PCPF such as age, sex, years with knee OA, radiographic severity of knee OA, knee pain, knee motion, and quadriceps strength were also recorded. The prevalence of self-reported knee instability was determined by calculating the proportion of subjects who reported each severity level of knee instability. Hierarchical regression analysis was performed to determine if the level of self-reported knee instability could predict the PCPF, even after accounting for the effects of the other variables.
Sixty-three percent of the subjects reported knee instability during activities of daily living, and 44% reported that instability affects their ability to function. The severity of self-reported knee instability was associated with the PCPF (eta2 = 0.40, P < 0.001), and after controlling for all other independent variables, significantly increased the prediction of the PCPF (r2 = 0.56, r2 change = 0.05; P < 0.001).
The results indicate that a substantial proportion of individuals with knee OA report episodes of knee instability during activities of daily living, and instability affects physical function beyond that which can be explained by contributions from other impairments such as knee pain, range of motion, and quadriceps strength. Knee instability is a problem that should be specifically addressed in rehabilitation programs and may require interventions beyond those that address pain, joint motion, and muscular strength, to maximize the effectiveness of rehabilitation for individuals with knee OA.