The contribution of leg press and knee extension strength and power to physical function in people with knee osteoarthritis: A cross-sectional study.

The purposes of this study were to 1) determine the additional contributions of leg press and knee extensor power, over and above that of strength, to the performance of physical function tasks in people with knee osteoarthritis, and 2) compare the ability of bilateral leg press to unilateral knee extensor strength and power to predict functional task performance. METHODS: A cross-sectional, exploratory study of 40 individuals with tibiofemoral knee osteoarthritis resulting in moderate impairments in physical function was conducted. Physical function (Get-up and Go, timed stair climb and descent, and five time chair rise) and muscle performance (leg press and knee extension strength and power) were assessed. RESULTS: After controlling for covariates and strength, leg press, but not knee extensor, power explained additional variance in physical function (11% and 21%). Conversely, adding strength to regression models including covariates and power did not consistently improve the prediction of physical function. Additionally, leg press power consistently explained more variance in physical function (44 to 57%) than involved (24 to 34%) or uninvolved (28 to 48%) knee extension power. CONCLUSIONS: Leg press power may be a more functionally relevant measure of muscle performance than knee extension strength in this population. Future studies should investigate the effectiveness of interventions specifically designed to improve leg press power in people with knee osteoarthritis.

Hip abductor strength in people with knee osteoarthritis: A cross-sectional study of reliability and association with function.

BACKGROUND: To investigate the clinical importance of hip abductor (HA) strength in people with knee osteoarthritis (OA), the purposes of this study were to 1) compare the association of HA strength and physical function to that of knee extensor (KE) strength and physical function, and 2) determine the reliability of the assessment of HA strength using a hand-held dynamometer. METHODS: Thirty-five individuals [58 years standard deviation 10 years old] with knee osteoarthritis participated. Physical function was assessed with performance-based [Get-Up and Go (GUG), stair climb and descent (SC), and five times chair rise (CR)] and self-reported (WOMAC function) measures. The relationship between strength and function was assessed using bivariate correlation and hierarchical multiple regression models. Reliability across sessions was assessed in 25 subjects. RESULTS: In the bivariate models, both KE and HA strength were both significantly associated with performance-based measures of function, but not WOMAC function. After controlling for anthropometric factors and KE strength in the hierarchical models, HA made significant independent contributions to the prediction of GUG and SC, but not CR or WOMAC function. The reliability of HA strength was excellent (ICC2, 3=0.94; 95% CI=0.86-0.97), while the minimum detectable change (MDC95) was 0.29Nm/kg (95% CI=0.23-0.41). CONCLUSION: HA strength can be reliably measured and is closely associated with functional performance in people with knee OA. CLINICAL RELEVANCE: These results provide preliminary evidence suggesting that HA strength may be an important rehabilitation target for the conservative management of knee OA.

Presence of medical comorbidities in patients with infected primary hip or knee arthroplasties.

Many older patients undergoing primary hip or knee joint arthroplasty surgery have multiple medical problems. In this retrospective case-control study, the authors examined the individual and cumulative effects of various types of medical comorbidities on the risk of developing prosthetic joint infection after surgery. Case and control patients were matched by age, sex, and procedure. Analysis was undertaken using crude odds ratios (ORs) and multiple logistic regression analysis. Fifty-one patients with 52 joint infections were identified. Both diabetes mellitus (OR, 3.91; P = .04) and total number of medical conditions (OR, 1.35; P = .005) were associated with higher risk of infection. This information allows the orthopedic surgeon to inform patients more fully regarding the risks of surgery, and promotes the reduction and optimization of medical comorbidities before surgery.