A functional model of the digital extensor mechanism: demonstrating biomechanics with hair bands

The action of muscles about joints can be explained through analysis of their spatial relationship. A functional model of these relationships can be valuable in learning and understanding the muscular action about a joint. A model can be particularly helpful when examining complex actions across multiple joints such as in the digital extensor mechanism of the hand. A functional model using two hair bands representing the components of the digital extensor mechanism is described. Through superimposition of the model over one's digit, the combined actions of metacarpophalangeal joint flexion and interphalangeal joint extension are clearly demonstrated. The model provides a conceptual demonstration to enhance understanding of this unique combination of muscle actions about multiple joints.