This condition is a stretching or tearing of the volar plate, which can allow the finger to hyperextend and can interfere with normal hand function. The volar plate is a strong ligamentous structure on the underside of the finger at the point where the proximal and middle phalanx bones meet, called the proximal interphalangeal joint (or PIP joint). The volar plate keeps the finger from bending backwards at the PIP joint, and, together with the collateral ligaments, stabilizes the PIP joint from displacement.
Conditions