Pharmacological and physical therapy are an essential conservative treatment option for knee osteoarthritis (OA). However, a group of patients with knee OA does not have adequate pain relief through the conservative treatment. Knee OA patients who have unique pain-related affective and/or cognitive characteristics may not be able to obtain adequate pain relief with conservative treatment. Early detection of patients with inadequate pain relief from conservative treatment allows for alternative treatment options to be considered, such as cognitive behavioral therapy. Therefore, in this study, we developed clinical prediction rules (CPRs) to identify knee OA patients who will likely obtain adequate pain relief with conservative treatment.

Subject were patients with symptomatic knee OA (n=88). The Numeric rating scale and the Knee Injury and Osteoarthritis Outcome Score scale were used to evaluate pain relief. Potential predictors for pain relief were depressive symptoms, self-efficacy, and pain catastrophizing. The classification and regression trees methodology was used to develop the CPR for predicting the presence or absence of pain relief at 1 and 3 months after the start of observation. The area under the receiver operating characteristic curve (AUC) was calculated to assess the accuracy of CPR developed.

The CPR at 1 month after the start of observation included the information about pain intensity at baseline, positive affect, and disease duration. The AUC of this CPR was 0.793 (95% confidential interval: 0.687–0.898). The CPR at 3 months after the start of observation included pain catastrophizing and self-efficacy. The AUC of this CPR was 0.808 (95% confidential interval: 0.682–0.934).

Information on the disease duration of knee OA, the intensity of pain, pain-related affective and/or cognitive characteristics can be used for developing CPR to predict pain relief in patients with knee OA receiving conservative treatment.