Anatomical Name of the Middle Knuckle of the Ring Finger
The middle knuckle of the ring finger is the proximal interphalangeal (PIP) joint.
Anatomical Structure
The proximal interphalangeal (PIP) joint is the articulation between the proximal phalanx (first bone of the finger) and the middle phalanx (second bone of the finger) 1.
This joint is distinct from the metacarpophalangeal (MCP) joint at the base of the finger (knuckle closest to the palm) and the distal interphalangeal (DIP) joint at the fingertip 1.
Clinical Relevance
PIP joint function is critical for proper finger and hand function, and injuries or arthritis of this joint can lead to considerable hand impairment 2, 3.
The joint is stabilized throughout its range of motion by surrounding structures including the proper collateral ligament, accessory collateral ligament, and volar plate 4.
The osseous anatomy of the PIP joint dictates the principles of motion, making understanding of its normal anatomy and biomechanics essential when treating pathology 4.
Imaging Considerations for PIP Joint Injuries
Standard radiographs (oblique, anteroposterior, and true lateral views) are recommended for all acute finger injuries to exclude fractures and foreign bodies, followed by systematic clinical examination 5.
MRI is ideal for evaluating tendon injuries and helping with surgical planning, and may be used to assess capsule and collateral ligament injuries of the PIP joint 1.
Dynamic ultrasound allows direct visualization of PIP joint malalignment in the absence of fracture 1.