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Interphalangeal Collateral Ligaments

ligamenta collateralia articulationum interphalangearum

The collateral ligaments at each IP joint prevent the lateral instability that would occur from side-to-side forces on the fingers during gripping, pinching, and contact. They are tightest in full flexion at the PIP joint and in full extension at the DIP joint, explaining the position-dependent instability testing. Collateral ligament injuries at the PIP joint are the most common ligamentous injury of the hand from sporting contact.

Anatomical Data

Attachments

Origin	Lateral condyles of the proximal phalanx (PIP) or middle phalanx (DIP)
Insertion	Lateral base of the middle phalanx (PIP) or distal phalanx (DIP) and the lateral volar plate margins

Biomechanics

Function & Actions

Actions	Primary resistance to varus and valgus stress at the IP joints maintain lateral joint stability through all positions

Resist radial and ulnar deviation forces at the finger interphalangeal joints throughout flexion and extension.

Clinical Relevance

Clinical Notes

Isolated PIP collateral ligament sprain produces localised lateral joint tenderness and swelling, confirmed by varus or valgus stress testing showing increased gapping compared to the adjacent finger. Most are managed with buddy taping to the adjacent finger for 3 to 6 weeks, allowing early motion. Complete collateral ligament tears at the PIP joint producing gross instability require surgical repair.

Pathology

Common Injuries & Conditions

PIP Collateral Ligament Sprain

Lateral finger ligament injury from varus or valgus force producing joint tenderness and limited swelling, managed with buddy taping for partial tears and surgical repair for complete instability.

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