THU0634-HPR KNEE EXTENSOR MUSCLE STEADINESS IN RELATION TO MAXIMAL TORQUE AND PHYSICAL FUNCTIONING IN PATIENTS WITH KNEE OSTEOARTHRITIS
Authors: A. Satam, M. Van der Leeden, A. De Zwart, S. Verberne, J. Schrijvers, J. Dekker, W. Lems, J. Haarlaar, M. Van der Esch
Journal: Annals of the Rheumatic Diseases (2020)

Background: Osteoarthritis (OA) of the knee is characterized by knee pain and limitations in daily activities. Muscle weakness is associated with these characteristics, quantified as maximal voluntary muscle torque (MVT). The quality of muscle contraction is presented by fluctuations observed on a torque-time curve and the extent of these fluctuations is referred to as muscle steadiness. Whether muscle steadiness is associated with maximal muscle torque and consequently with pain and activity limitations is unknown. Objectives: To determine the association of knee extensor muscle steadiness with MVT and to explore the association of muscle steadiness with physical functioning in subjects with knee OA. Methods: Baseline data of 172 patients out of 177 patients with knee OA, who participated in the VIDEX trial (trial registration number, NL47786.048.14), were used for this study. Maximal voluntary knee extension torque (MVT) was assessed using an isokinetic dynamometer. Torque-time curve data were processed into (i) coefficient of magnitude of torque variance (CV) in percentage (%), (ii) frequency of torque variance as peak power frequency (PPF) in Hertz (Hz) and (iii) MVT in Newton meters (Nm). Physical functioning was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, the Get-Up &amp; Go (GUG) test, the 6-minute walk test (6MWT) and the Stair climb up &amp; down test. Correlation and Regression analyses were performed to determine associations. Sex, age, BMI, KL-grade, knee alignment and pain were considered as potential confounders. Results: Lower CV and PPF, reflecting better muscle steadiness, were significantly associated (p&lt; 0.01 and p&lt;0.05, respectively) with higher MVT, but associations were weak. Regression analyses showed a significant association of lower CV with better physical functioning on the WOMAC (p&lt;0.05), also after correction for relevant confounders. The association with WOMAC was confounded by pain, but not by sex, age and BMI. No associations of CV with the GUG test, the 6MWT and the Stair climb up &amp; down test were found. PPF was not significantly associated with physical functioning. Conclusion: This is the first explorative study of muscle steadiness in relation to physical functioning in knee OA patients. Muscle steadiness is, to some extent, related to better physical functioning, but this is not consistent across all measures of physical functioning in this study. There seems to be some relationship, but it is weak and needs further exploration. No previous studies comparing clinical scores to muscle steadiness in knee OA were found to compare our results. Studies on muscle steadiness are needed to improve our understanding on this aspect of muscle torque. References: N/A Disclosure of Interests: Anuja Satam: None declared, Marike van der Leeden: None declared, Arjan de Zwart: None declared, Simon Verberne: None declared, Jim Schrijvers: None declared, Joost Dekker: None declared, WIllem Lems Grant/research support from: Pfizer, Consultant of: Lilly, Pfizer, Jaap Haarlaar: None declared, Martin van der Esch: None declared