The WOMAC (Western Ontario and McMaster Universities Osteoarthritis) Pain Scale estimates knee pain severity with activities of daily living. Utilizing a causal modeling technique, the pain effect in other body regions on WOMAC pain scores has not been monitored. According to the study results, cross talk may be a source of error in the WOMAC Pain Scale (specifically for subjects with more number of painful body regions and when the pain severity of contralateral knee joint is high).

This study aimed to assess the “cross-talk”phenomenon (whether pain in other areas of the body impacts WOMAC pain scores).

Using the data available from OAI (the Osteoarthritis Initiative) and the MOST (Multicenter Osteoarthritis Study), the cross-sectional datasets were generated. The generic hip, knee, foot, ankle, back pain measures, and the WOMAC Pain Scale were also incorporated. Using the three nested regression models grounded in causally based classical test theory, the cross-talk range was assessed. To monitor the presence of cross-talk, enhancements in R2 (coefficient of determination) across the 3 models were utilized.

In both OAI and MOST datasets, causal modeling provided evidence of cross-talk. For example, in OAI, multiple statistical models demonstrated a substantial elevation in R2 values as additional pain areas were added to the models.

When interpreting WOMAC pain scores, clinicians should be aware of the threat to score interpretation and the requisition to consider the extent of pain in other body regions.