Reports of joint instability in knee osteoarthritis: Its prevalence and relationship to physical function

Abstract

Objective. 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. Methods. 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. Results. 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 (eta 2 ‫؍‬ 0.40, P < 0.001), and after controlling for all other independent variables, significantly increased the prediction of the PCPF (r 2 ‫؍‬ 0.56, r 2 change ‫؍‬ 0.05; P < 0.001). Conclusion.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.

Association of lower muscle strength with self‐reported knee instability in osteoarthritis of the knee: Results from the Amsterdam Osteoarthritis Cohort

“…In our study, a substantial proportion (67%) of the knee OA population reported knee instability, which is similar to earlier studies (2)(3)(4)(5)(6). A large number of knee OA patients may therefore be in need of treatment specifically aiming to improve knee stability.…”

“…Muscles around the knee are presumed to be major stabilizers of the knee joint (20,22) and are considered to play a crucial role in knee stability in patients with knee OA (2,8,14,17,19). The presence of episodes of knee buckling has been found to be related to weaker lower extremity muscle strength in a large study cohort (but not exclusively knee OA patients) (1).…”

“…Selfreported knee instability has been operationalized by the sensation of buckling, shifting, or giving way of the knee (1). Approximately 60 -80% of patients with knee osteoarthritis (OA) report knee instability (2)(3)(4)(5)(6). Knee OA patients reporting knee instability have more severe activity limitations (2,4) than knee OA patients without this sensation.…”

“…Knee instability has been suggested to be a multifactorial problem (1,2,4,14). Biomechanical impairments such as muscle weakness, impaired proprioceptive accuracy, and high laxity, which are frequently present in knee OA patients (15)(16)(17)(18), have been regularly hypothesized as important causal factors in self-reported knee instability (1,2,4 -6,13,14,19).…”

“…Strong lower extremity muscles are suggested as being structures able to stabilize the knee, even when proprioceptive accuracy is impaired or laxity is high (2,8,14,17,19). Studies by van der Esch et al (14,19) in knee OA patients showed that in persons with impaired proprioceptive accuracy or high laxity, muscle strength was more strongly related to activity limitations than in persons with adequate proprioceptive accuracy or low laxity.…”