Injuries to the thumb ulnar collateral ligament (UCL) are common. Failure to address the ensuing laxity of the metacarpophalangeal joint can lead to compromised grip and pinch, pain, and ultimately osteoarthritis.

Patients who have sustained an acute injury commonly recount a traumatic episode with an accompanying onset of pain and swelling, whereas those with chronic injuries may present with less specific symptoms.

The diagnosis of UCL injury relies primarily on the clinical examination of the patient.

Instability to valgus stress with the lack of a firm end point is a strong indicator of complete rupture of the UCL. Ultrasonography, MRI, and plain films can be useful adjuncts.

Nonoperative treatment is reserved for incomplete ruptures of the thumb UCL.

Operative intervention is typically performed for complete ruptures.

The goal of surgery is to restore the anatomic position of the ligament, thus providing stability to the metacarpophalangeal joint and allowing for protected range of motion early in the rehabilitation period.

Both repair of acute ruptures and reconstruction for chronic injuries yield excellent results. Complications are rare and most patients show preservation of motion, key pinch, and grip strength.

Range of motion exercises early in the rehabilitation phase help to ensure a positive outcome.