Knee Pain Patterns and Associations with Pain and Function in Persons with or at Risk for Symptomatic Radiographic Osteoarthritis: A Cross-sectional Analysis

OBJECTIVE: Knee pain location is routinely assessed in clinical practice. We determined the patterns of patient-reported pain locations for persons with knee osteoarthritis (OA). We also examined associations between knee pain patterns and severity of self-reported pain with activity and self-reported functional status. METHODS: The Osteoarthritis Initiative data were used to examine reports of pain location (localized, regional, or global) and type and extent of knee OA. Multivariable ANCOVA models were used to determine associations between the Knee Injury and Osteoarthritis Outcome Survey (KOOS) Pain and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Function scales and pain location after adjusting for potential confounding. We also used radar graphs to illustrate pain patterns for various locations and severity of knee OA. RESULTS: Radar graphs of 2696 knees indicated that pain pattern and location and extent of knee OA demonstrate substantial overlap. An interaction between race and pain location was found for WOMAC Function, but not for KOOS Pain scores. Global knee pain was associated (p < 0.001) with substantially worse function (by 6.5 points in African Americans) compared with pain that was localized. Knee pain reported as global was independently associated (p < 0.001) with clinically important lower (worse by 3.9 points) KOOS Pain scores compared with pain that was localized. CONCLUSION: Pain patterns are not useful for inferring potential location or severity of knee OA in individual patients, but knee pain patterns that are global are independently associated with worse pain and function compared with localized pain, and associations differ for function based on race.