Factors associated with self-rated difficulty to descend stairs in persons with knee osteoarthritis

Background Difficulty descending stairs is common in persons with knee osteoarthritis (OA). Clinically, it is important to know if and how this is explained by objectively measured difficulty to descend stairs, muscle weakness, pain, fear of movement, or knee joint status. Objective To identify the potential of these factors to explain self-reported difficulty descending stairs. Design Cross sectional, case-control. Setting Hospital outpatient and physiotherapy clinic. Participants Twenty-eight men and women with knee OA (age 62.2 SD 5.9 years) and 31 controls (age 50.0 SD 8.5 years). Intervention Not applicable. Main outcome measures Using multivariate statistics, group comparisons were made for lower extremity kinematics (incorporating hip, knee, and ankle angles) and stance time in stair descent and lower extremity muscle strength. Then, a stepwise linear regression analysis was performed within the OA group to explain self-reported difficulties in stair descent where pain, kinesiophobia, radiographic signs, and outcomes that differed from controls for stair-descent kinematics and muscle strength were independent variables. Results Multivariate statistics showed that the OA group displayed different all-over lower extremity kinematics (F8,42 = 2.44 p = .029, η2 = 0.32) and a longer stance time (F3,50 = 6.46; p = .001, η2 = 0.28) in stair descent and lower muscle strength (F7,47 = 2.39; p = .035, η2 = 0.26) compared to controls. Regression analysis within the OA group to explain self-rated difficulties to descend stairs showed that the strongest association with kinesiophobia (ß = 0.607, p = .001) that combined with pain last week and radiographic signs explained almost 100% (ß = 0.972). Stair descent kinematics and strength variables that differed between groups did not explain self-rated difficulties to descend stairs. Conclusion Kinesiophobia and pain rather than stair-descent kinematics and reduced muscle-strength explained self-rated difficulties in stair descent in the OA group.