The effect of hip adduction angle on patellar position measured using real time ultrasound scanning

IntroductionThere are limited in vivo studies investigating the influence of the Iliotibial Band (ITB) on patellar position, despite numerous references in the literature to this relationship. The purpose of this study was to investigate how the ITB influences patellar position, in vivo, indirectly through alteration of frontal plane hip position.MethodTwelve healthy, asymptomatic, male subjects (age 23 ± 2.6 years) had their patellar position examined using real time ultrasound scanning. The knee was passively placed into 20° flexion and combined with hip neutral, 20° hip adduction and 20° hip abduction. Mean patellar position (distance from the lateral border of the patella to the edge of the intersection of the trochlear groove and lateral femoral condyle) was measured, with the smaller values representing a position whereby the patella is drawn more laterally and closer to the lateral femoral condyle.ResultsMean patellar position for neutral was 8.1 mm (± 1.72 mm). Following 20° hip abduction the mean patellar position was 8.9 mm (± 1.79 mm), this was a statistically significant change in patellar position (p = 0.003). Following 20° hip adduction the mean patellar displacement was 7.3 mm (± 1.4 mm) which, again, was a statistically significant change in patellar position (p = 0.009). The results indicate that with the hip adduction the patella was positioned significantly more laterally (smaller value for distance).DiscussionThe results of this study support the hypothesis that hip adduction which is likely to create loading and lengthening of the ITB causes significantly greater lateral displacement of the patella, than when the hip is abducted and the ITB unloaded.Level of evidence: 2b individual cohort study.