Abstract
Abstract
Purpose
This study aimed to characterize three-dimensional course and orientation of the proximal aponeurosis of the biceps femoris long head (BFlh) and examine whether local aponeurosis orientations vary with knee-joint angle and relate to fascicle architecture under passive conditions.
Methods
Three-dimensional ultrasonography of the passive BFlh was performed in eleven healthy adults with knee flexion of 0° and 30° and hip in neutral (0°). Aponeurosis orientation was quantified across the visible segmented portion relative to the most transverse proximal slice (0%) within each knee-angle condition and summarized within five longitudinal sections. Fascicle length (FL) was assessed using a two-segment approach and pennation angle (PA; local fascicle–aponeurosis angle) relative to proximal and distal aponeuroses.
Results
Proximal aponeurosis exhibited a twisted three-dimensional course with substantial inter-individual variability. Local orientation showed a significant section × knee angle interaction (p = 0.016), although overall aponeurosis orientation did not differ between knee angles. Fascicles were shorter at 30° (− 8.8% ± 3.4%). PA-distal was greater than PA-proximal (p
Conclusion
BFlh proximal aponeurosis showed locally varying three-dimensional orientation that was largely maintained across passive knee flexion. Associations with fascicle architecture were limited and configuration-dependent, with no association between knee-angle-dependent changes in aponeurosis orientation and changes in FL or PA.