Rectus femoris knee muscle moment arms measured in vivo during dynamic motion with real-time magnetic resonance imaging.
Moment arms represent a muscle's ability to generate a moment about a joint for a given muscle force. The goal of this study was to develop a method to measure muscle moment arms in vivo over a large range of motion using real-time magnetic resonance (MR) imaging. Rectus femoris muscle-tendon lengths and knee joint angles of healthy subjects (N = 4) were measured during dynamic knee joint flexion and extension in a large-bore magnetic resonance imaging (MRI) scanner. Muscle-tendon moment arms were determined at the knee using the tendon-excursion method by differentiating measured muscle-tendon length with respect to joint angle. Rectus femoris moment arms were averaged across a group of healthy subjects and were found to vary similarly during knee joint flexion (mean: 3.0 (SD 0.5) cm, maximum: 3.5 cm) and extension (mean: 2.8 (SD 0.4) cm, maximum: 3.6 cm). These moment arms compare favorably with previously published dynamic tendon-excursion measurements in cadaveric specimens but were relatively smaller than moment arms from center-of-rotation studies. The method presented here provides a new approach to measure muscle-tendon moment arms in vivo and has the potential to be a powerful resource for characterizing musculoskeletal geometry during dynamic joint motion.
Niccolo M
NM
Fiorentino
Jonathan S
JS
Lin
Kathryn B
KB
Ridder
Michael A
MA
Guttman
Elliot R
ER
McVeigh
Silvia S
SS
Blemker
D000328:Adult; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D009068:Movement; D052097:Quadriceps Muscle / Q000502:physiology*; D016059:Range of Motion, Articular; D013997:Time Factors