A clinical prediction rule for identifying patients with patellofemoral pain who are likely to benefit from foot orthoses: a preliminary determination.

OBJECTIVE To develop a clinical prediction rule to identify patients with patellofemoral pain (PFP) who are more likely to benefit from foot orthoses. DESIGN Posthoc analysis of one treatment arm of a randomised clinical trial. SETTING Single-centre trial in a community setting in Brisbane, Australia. PARTICIPANTS 42 participants (mean age 27.9 years) with a clinical diagnosis of PFP (median duration 36 months). INTERVENTIONS Foot orthoses fitted by a physiotherapist. MAIN OUTCOME MEASURES Five-point global improvement scale at 12-week follow-up, dichotomised with marked improvement equalling success. RESULTS Potential predictor variables identified by univariate analyses were age, height, pain severity, anterior knee pain scale score, functional index questionnaire score, foot morphometry (arch height ratio, mid-foot width difference from non-weight bearing to weight bearing) and overall orthoses comfort. Parsimonious fitting of these variables to a model that explained success with orthoses identified the following: age (>25 years), height (<165 cm), worst pain visual analogue scale (<53.25 mm) and a difference in mid-foot width from non-weight bearing to weight bearing (>10.96 mm). The pretest success rate of 40% increased to 86% if the patient exhibited three of these variables (positive likelihood ratio 8.8; 95% CI 1.2 to 66.9). CONCLUSION Post-hoc analysis identified age, height, pain severity and mid-foot morphometry as possible predictors of successful treatment of PFP with foot orthoses, thereby providing practitioners with information for prescribing foot orthoses in PFP and stimulating further research.