Using Hierarchical Linear Modeling to Explore Predictors of Pain After Total Hip and Knee Arthroplasty as a Consequence of Osteoarthritis

Hierarchical linear modeling was used to establish differences in, and the average pattern of, recovery of the pain subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and 2 composite performance-specific measures of pain as well as to determine if significant individual variations exist in the growth curves for each measure. Predictors of postoperative pain were also of interest. One hundred forty-seven patients undergoing unilateral primary hip or knee arthroplasty completed 4 performance measures-self-paced 40-m walk, timed up and go, stair test, and 6-minute walk-and the WOMAC prearthroplasty and at multiple points in time between 2 and 27 weeks postarthroplasty. Although patients reported different levels of postoperative pain initially, similar recovery patterns were noted. Predictive variables were found to be site of joint arthroplasty and WOMAC prearthroplasty pain scores for the WOMAC pain subscale, the site of joint arthroplasty and sex for the first composite pain score, and sex for the second composite.