Normative data of frontal plane patellar alignment in athletes.

OBJECTIVE: The objective of this study was to provide normative data of frontal plane patellar alignment according to McConnell and Arno angles, verify the association between theses angles and identify the presence of patellar rotation in different sports. DESIGN: Cross-sectional. PARTICIPANTS: Nine participants (18 knees) were assessed in a preliminary study to verify the intra and inter-examiner reliabilities of the patellar alignment measures. In the main study, 230 volleyball, basketball, gymnastics and soccer athletes (460 knees) were evaluated in order to obtain normative data of patellar alignment. MAIN OUTCOME MEASURES: Frontal plane patellar alignment (McConnell and Arno angles) measured in standing position by means of photogrammetry. RESULTS: The standardized method demonstrated intra and inter-examiner reliability coefficients varying from .85 to .98. The mean McConnell and Arno angles were 2.05° (±5.9) and 2.89° (±7.57), respectively. A low association was observed (r = .189, p < .0001) between these angles. There was a difference in distribution of medial and lateral rotations, according to the McConnell angle, between different sports (p < .014). CONCLUSIONS: The proposed procedure for measuring patellar alignment according to McConnell and Arno angles proved to be highly reliable. This made possible the establishment of normative data in a large sample of healthy athletes.