This patient presented with thumb trauma due to a fall on the ground. Ultrasound shows an absent ulnar collateral ligament along with the formation of a hypoechoic pseudomass abutting metacarpal bone. When the ruptured ligament is displaced over adductor pollicis aponeurosis; there is a pseudomass formation proximal to the joint line and abutting metacarpal bone. It is called a Stener lesion. No surgical follow-up is available.

Ulnar collateral ligament of the thumb shows three types of injury:

1. Avulsion of distal end of ligament along with a bone flake. There is easily seen on radiographs.

2. Tear of the collateral ligament (usually the distal end) with a ligament in situ - deep to adductor pollicis aponeurosis. There is no pseudomass formation in this case.

3. Ruptured and displaced ligament over aponeurosis forming a pseudomass. It is known as a Stener lesion. This requires surgical treatment.