Aspects of the extensor assembly of the finger during interphalangeal flexion

Abstract

In the extended finger the lateral bundles (lateral bands) of the extensor assembly along the trochlea of the PIP (proximal interphalangeal) joint are located between frontal and sagittal planes. During PIP flexion, the lateral bundles “tilt” somewhat towards sagittal planes, thus assuming slightly more palmar positions. They thereby “release” the extended DIP (distal interphalangeal) joint, enabling this joint to be flexed as well. In subsequent full DIP flexion, the lateral bundles obtain their nearly sagittal positions, running along the trochlea of the flexed PIP joint.