The sprain usually occurs at the base of the thumb (the MCPJ), caused by the stock hyperextending the joint usually during a fall. The ligament injured is the ulnar collateral ligament (UCL). In some cases the UCL will pull off a small bony 'avulsion fracture'.
The UCL at the MCPJ is essential in providing stability to the thumb. Without it even holding a pen is difficult!
A skilled hand therapist or specialist can determine stability by stress testing the joint. And it is always advisable to have an x-ray or diagnostic ultrasound, to determine whether there is a fracture. The severity of the injury will determine the course of treatment. In some cases a fracture might have moved and an operation will be required.
In most cases a hand therapist can fix Skier's Thumb by making a thermoplastic splint that will hold the joint in a safe position whilst the ligament +/- bone heals. Taping techniques can also be used during the splint weaning phase, to help get you back to work / sports quickly & safely. And we will always give you exercises to stabilise the soft tissues around the injured, and surrounding joints.
Keep those thumb tips safe!