Background/Purpose: Back pain, most commonly occurring in the lower back, is a prevalent condition and common reason for both decreased function and quality of life. The influence of back pain on physical function among patients with osteoarthritis (OA) has received little attention.  This study examined association of back pain with functional outcomes in patients with hip and / or knee OA.

Methods:

Participants (n=300) were patients enrolled in a clinical trial of a combined patient and provider intervention for managing OA at the Durham Veterans Affairs Medical Center (mean age = 61.1 (SD 9.2), 90.7% male, 50.0% non-white – primarily African American).  All measures were taken from baseline surveys and tests. Self-reported presence of back pain was measured with a single item from the Self-Administered Comorbidity Questionnaire.  Functional outcomes included the Satisfaction with Physical Function Questionnaire (scores range -3 to +3, with higher scores indicating greater satisfaction), disease specific knee and/or hip function (Western Ontario and McMasters University Osteoarthritis Index physical function subscale; range 0-68), and the Short Physical Performance Battery (SPPB) consisting of walking, balance and chair stands tests, with scores ranging from 0 (worst performance) to 12 (best performance). Simple linear regression models examined the association of back pain with each functional measure (separately), and then multivariable models were fit, including all covariates. Covariates included participant age, race (white vs. non-white), gender, self-rated health (excellent, very good, or good vs. fair or poor) and number of joints with knee and/or hip OA (1-4).

Results:

Back pain was present in 75.3% of patients.  In bivariate analyses, back pain was associated with less Satisfaction with Physical Function (b= -0.64; 95% CI -1.06, -0.22; p<0.01), worse WOMAC function scores (b= 5.10; 95% CI = 1.70, 8.50; p=0.003), and worse SPPB scores (b= -0.73; 95% CI -1.31, -0.15; p=0.01). In the multivariable models, back pain remained significantly associated with Satisfaction with Physical Function scores (b= -0.49; 95% CI -0.89, -0.10; p=0.02) and WOMAC physical function scores (b= 4.1; 95% CI 0.90, 7.30; p=0.01), but not SPPB scores (b= -0.51; 95% CI -1.1, 0.04; p=0.07).

Conclusion: Among patients with hip and knee OA, back pain was highly prevalent.  Back pain was associated with worse functional outcomes, specifically Satisfaction with Physical Function and WOMAC function scores. These results highlight that back pain is associated with lower extremity functional limitations above and beyond decreased function related to knee and/or hip OA. Because of its high prevalence and added impact on physical function, back pain is an important issue to identify and address among patients with OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-back-pain-with-functional-limitations-in-patients-with-knee-and-hip-osteoarthritis/