A novel patellofemoral scoring system for patellofemoral joint status.

BACKGROUND We were not aware of a well-validated patellofemoral joint-specific scoring system. We performed this study to develop and validate a scoring system (Samsung Medical Center [SMC] patellofemoral scoring system) suitable for the evaluation of patellofemoral joint status. METHODS We recruited 179 individuals consisting of a study group of 123 patients with anterior knee pain but without pain in another part of the knee, twenty-eight patients with knee pain other than anterior knee pain (group A), and twenty-eight healthy volunteers without knee pain (group B). Items in the development of the scoring system that showed a significant difference between the study group and group A and between the study group and the group B were selected. Test-retest reliability was measured by intraclass correlation coefficient, internal consistency was measured by the Cronbach alpha, content validity was assessed by ceiling and floor effects, and construct validity was determined by the association of the Feller scores and the SMC patellofemoral scores. RESULTS After the item verification process, seventeen items (eight items for patellofemoral pain and nine items for patellofemoral function) were selected. Test-retest reliability for overall SMC patellofemoral scores showed excellent reliability (intraclass correlation coefficient, 0.85), and internal consistency was excellent (Cronbach alpha, 0.97). Floor and ceiling effects were acceptable (<30%) for all the items of the SMC patellofemoral scoring system, except one: sitting down on a chair, in the patellofemoral function score. The SMC patellofemoral scores showed moderate correlation with the Feller scores (ρ = -0.45). CONCLUSIONS AND CLINICAL RELEVANCE The SMC patellofemoral score is a novel scoring system that distinguishes patients with anterior knee pain or patellofemoral dysfunction from patients with knee pain or dysfunction arising from other knee problems, and from those without knee pain. The reliability and validity of the SMC patellofemoral scoring system were verified in the present study.