Figure 1.

The figure illustrates the 3 models used to test for causal associations between a variety of pain measures and the WOMAC pain score. Model 1 described the association between WOMAC pain and the unidimensional generic pain score for the involved knee. Model 2 included both the involved generic knee pain score and all potential moderators (ie, a composite lower extremity pain score not including both knees, a contralateral generic knee pain score, and a back pain score). Model 3 included the involved generic knee pain score, and interactions among all potential moderators (ie, a composite lower extremity pain score not including both knees, a contralateral generic knee pain score, and a back pain score).