Dynamic ultrasound measurement of patellar lateral tracking

This study used ultrasound scanning to investigate the patellar medial/lateral shift (patellar lateral tracking) in sitting flexion/extension and squatting. A femoral clamp was used to hold the ultrasound probe during testing. In sitting, the patella moved medially from 90° to 20° knee flexion, then turned laterally to terminal extension. Similar tracking pattern was observed for squatting. ANOVA revealed that the patellar lateral position was greatly affected by the movement pattern (p<0.0005), and was also influenced by the gender for maximum medial position (p<0.05). Height, patellar width and patellar length were found to have a moderate to good correlation to the patellar lateral tracking. Student t-test showed good inter- and intra-rater test-retest relationship (p<0.05) for patellar tracking measurement. This is the first dynamic patellar tracking evaluation in vivo using a non-invasive method. Further research is necessary for the accuracy and validity of this method, and for evaluation of patellofemoral patients.