Composite measures of multi-joint symptoms, but not of radiographic osteoarthritis, are associated with functional outcomes: the Johnston County Osteoarthritis Project.

Purpose: To determine associations between multiple joint symptoms and radiographic osteoarthritis (rOA) and functional outcomes.
Method: Complete cross-sectional data for multi-joint symptoms and radiographs, Health Assessment Questionnaire (HAQ) scores, and gait speed were available for 1307 Johnston County Osteoarthritis Project participants (34% men, 32% African American, mean age 66 years). Factor analysis of symptom scores and radiographic grades for the lumbosacral spine, bilateral hands, knees, and hips provided composite scores. Regression models were used to determine associations between composite scores, HAQ, and gait speed, adjusting for age, body mass index, gender, and race.
Results: Five rOA factors were identified: (1) IP/CMC factor (carpometacarpal [CMC] and all interphalangeal [IP] joints); (2) MCP factor (metacarpophalangeal joints 2-5); (3) Knee factor (tibiofemoral and patellofemoral joints); (4) Spine factor (L1/2 to L5/S1); and (5) Symptom factor. After adjustment, only the Symptom composite was significantly associated with HAQ and gait speed; a 1-standard deviation increase in Symptom score was associated with 9 times higher odds of having poorer function on the HAQ (odds ratio 9.32, 95% confidence interval [CI] 6.80, 12.77), and a clinically significant decline in gait speed (0.06 m/s, 95% CI -0.07, -0.05).
Conclusions: A novel Symptom composite score was associated with poorer functional outcomes.
Implications for Rehabilitation: Osteoarthritis (OA) commonly affects multiple joints and is the most common form of arthritis. Symptomatic assessments, which can be easily executed by rehabilitation practitioners, are more closely related to self-reported and performance-based functional status than are less accessible and more costly radiographs. Symptomatic assessments are likely to be more informative for understanding, treating, and potentially preventing functional limitations than radiographic assessments.