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