The difference in a clinical measure of patella lateral position between individuals with patellofemoral pain and matched controls

STUDY DESIGN: Cross-sectional matched-pairs design. OBJECTIVE: To investigate if differences existed in the medio-lateral position of the patella between subjects with patellofemoral pain (PFP) and matched controls. BACKGROUND: The assessment of patella position is often proposed as an essential aspect of clinical examination of individuals with PFP. To date, only 1 clinical method of assessing lateral patella position has been intensively investigated. Although there is a growing body of evidence on the reliability and validity of this method, no studies have investigated differences in patella position between individuals with PFP and controls. METHODS AND MEASURES: Twelve female subjects with PFP and 12 matched controls (mean +/- SD age, 21.9 +/- 2.6 years) were assessed for medio-lateral patella position with the knee in 20 of flexion. Differences between groups were investigated with independent-groups t tests. RESULTS: All subjects were found to have a laterally located patella. The mean +/- SD lateral position for the individuals in the PFP group was 7.5 +/- 2.6 mm compared to 3.8 +/- 2.4 mm for the control group. This difference was statistically significant (P =.019). Intratester reliability of the measurement of patellar position, calculated using intraclass correlation model 3,1 was 0.86. CONCLUSION: Using this method of assessing patella position, the patella of individuals with PFP was significantly more laterally located than the patella of those in a matched control group.