Hip Range of Motion and Strength Predict 12‐Month Physical Function Outcomes in Older Adults With Chronic Low Back Pain: The Delaware Spine Studies

OBJECTIVE: The objective of this study was to investigate whether poor hip range of motion (ROM) and strength predict 12‐month physical function decline among older adults with chronic low back pain (LBP) and whether hip osteoarthritis modifies those relationships. METHODS: At baseline, passive ROM and strength measurements were taken for hip flexion, extension, abduction, adduction, internal rotation, and external rotation; ultrasound images and self‐reported symptoms were used to evaluate hip osteoarthritis presence (eg, osteophytes and hip pain). At baseline and 12 months, performance‐based (repeated chair rise, self‐selected gait speed, 6‐minute walk test [6MWT]) and self‐reported (Quebec LBP Disability Questionnaire, Late‐Life Function & Disability Instrument [LLFDI] basic and advanced lower extremity scales) physical function outcomes were assessed. Regression models were constructed for each outcome predicted by baseline hip ROM and strength measures, with adjustment for potential covariates. To avoid collinearity, hip ROM and strength measures with the strongest unadjusted correlations were included in final models. The hip osteoarthritis presence by hip ROM/strength interaction was also explored. RESULTS: Hip abduction strength predicted repeated chair rise (β = −0.297, P < 0.001), gait speed (β = 0.160, P = 0.003), 6MWT (β = 0.159, P ≤ 0.001), Quebec LBP Disability Questionnaire (β = −0.152, P = 0.003), and LLFDI basic lower extremity scale (β = 0.171, P = 0.005) outcomes. Regarding hip ROM, extension predicted repeated chair rise (β = −0.110, P = 0.043) and LLFDI advanced lower extremity scale (β = 0.090, P = 0.007) outcomes, external rotation predicted gait speed (β = 0.122, P = 0.004) outcomes, and abduction predicted LLFDI basic lower extremity scale (β = 0.114, P = 0.026) outcomes. The hip osteoarthritis interaction was not significant for any model. CONCLUSION: Reduced hip strength and ROM predict physical function decline; hip osteoarthritis presence may not modify these relationships.