Development of a clinical prediction rule to identify patients with knee pain and clinical evidence of knee osteoarthritis who demonstrate a favorable short-term response to hip mobilization

Background and Purpose The primary purpose of this study was to develop a clinical prediction rule (CPR) for identifying patients with knee pain and clinical evidence of knee osteoarthritis (OA) with favorable short-term response to hip mobilizations. The secondary purpose was to determine the predictive validity of individual clinical tests for identifying these same patients. Subjects and Methods Sixty subjects with knee OA, aged 51 to 79 years, completed self-report questionnaires, a clinical examination of the hip and knee, and functional tests and were treated with 4 hip mobilizations. Follow-up, testing was completed 2 days later. The reference criterion for determining a favorable response was either (1) a decrease of at least 30% on composite Numerical Pain Rating Scale score obtained during functional tests or (2) a Global Rating of Change Scale score of at least 3. Results The CPR developed in this study comprised 5 variables: (1) hip or groin pain or paresthesia, (2) anterior thigh pain, (3) passive knee flexion less than 122 degrees, (4) passive hip medial (internal) rotation less than 17 degrees, and (5) pain with hip distraction. Based on the pretest probability of success (68%), the presence of one variable had a positive likelihood ratio of 5.1 and increased the probability of a successful response to 92% at 48-hour follow-up. If 2 variables were present, the Positive likelihood ratio was 12.9 and the probability of success increased to 97%. Discussion and Conclusion The results suggest that the CPR developed in this study could improve clinicians' decision making and efficiency in examining and treating patients with knee OA.