The Middle Joint of the Finger
The middle joint of the finger is the proximal interphalangeal (PIP) joint, which connects the proximal phalanx to the middle phalanx 1.
Anatomical Context
The PIP joint is one of three primary joints in each finger (excluding the thumb):
- Distal interphalangeal (DIP) joint - the joint closest to the fingertip 1
- Proximal interphalangeal (PIP) joint - the middle joint 1
- Metacarpophalangeal (MCP) joint - the knuckle at the base of the finger 1
Clinical Significance
The PIP joint is particularly important clinically because:
- It is highly susceptible to injury and fracture-dislocation due to the long leverage of the finger and relatively small joint diameter 2
- It commonly develops osteoarthritis, often presenting with Bouchard nodes (bony enlargement at the PIP joint) 1
- Injuries frequently result in stiffness and contractures if not properly managed, as the joint is prone to tendon adhesion 2, 3
- Gross instability occurs when collateral ligaments and volar plate are disrupted along with at least 30% of the volar lip of the middle phalanx 4
Imaging Evaluation
When PIP joint pathology is suspected:
- MRI is the ideal modality for soft tissue injuries including collateral ligament and volar plate tears, with sensitivity for capsular injuries assessed through dedicated protocols 1
- Standard radiographs are first-line for fractures and osteoarthritis, showing joint space narrowing, osteophytes, and subchondral changes 1
- Dynamic ultrasound can directly visualize joint malalignment in the absence of fracture 1