summary Digital Collateral Ligament Injuries result from direct trauma to the digit injuring the radial or ulnar collateral ligaments. Diagnosis is made clinically and MRI may be required for confirmation. Treatment is nonoperative with buddy splinting with the exception of radial collateral injury to the index finger which requires surgical repair. Epidemiology Incidence rare < 1 per 100,000 annually Etiology Mechanism depends on the joint involved usually the result of a "jammed finger" doral or volar dislocation events can tear one or both of the collateral ligaments Anatomy Collateral ligaments of the digits located on the lateral aspect of the DIP, PIP and MCP joints crucial for opposing pinch stability Presentation Symptoms pain at involved joint instabilty with pinch once pain resolved Physical exam inspection swelling at involved joint deformity of joint provocative tests varus and valgus stress tests Imaging Radiographs recommended views PA lateral oblique varus/valgus stress views may aid in diagnosis MRI indicated if equivocal physical exam findings Treatment Nonoperative buddy taping for 3 weeks indications simple tears buddy taping for 6 weeks indications complete tears Operative collateral ligament repair indications radial ligament injuries of index finger (ligament needed for pinch stability)