Collateral Ligaments of the Proximal Interphalangeal Joints, Anterior View

Description

Running along the radial and ulnar sides of each proximal interphalangeal (PIP) joint, the proper collateral ligaments appear as stout bands spanning from the dorsal tubercles of the proximal phalangeal heads to the lateral aspects of the bases of the middle phalanges. From the anterior aspect of a male hand skeleton, the proximal, middle, and distal phalanges align in longitudinal rays distal to the metacarpals, with the PIP articulations centered between the proximal and middle phalanges. The volar plates lie on the palmar side of these joints (deep to the capsule), while the collateral ligament complexes sit lateral to the joint capsule and define the margins of each hinge joint. Bone landmarks are clear. Functionally, the PIP collateral ligaments tighten with flexion and relax in extension, a relationship that explains why lateral stress testing in clinical exam changes with joint position and why prolonged immobilization in flexion can lead to stiffness. Forced ulnar or radial deviation at the PIP joint, common in ball sports and falls, can sprain or avulse these ligaments at their phalangeal attachments, sometimes with a small bony fragment visible on radiographs. This anterior presentation also supports teaching the difference between PIP collateral injury and the more distal distal interphalangeal (DIP) mallet mechanism, as well as the separate collateral system of the metacarpophalangeal joints. Hand anatomy and orthopaedics courses can use this plate to orient learners to the capsuloligamentous constraints that guide PIP flexion and resist coronal plane instability. It also fits operative and rehab-focused content on PIP sprain management, collateral ligament repair, and post-injury splinting positions, where accurate side-to-side anatomy matters for restoring stable pinch and grip. Anatomical accuracy verified by SciePro's Medical Advisory Board.