What to Know About a Sprained Thumb

Medically Reviewed by Dany Paul Baby, MD on October 19, 2022
5 min read

A sprained thumb occurs when you injure the soft tissue or ligaments that connect your thumb to your hand. The most commonly injured ligament in the thumb is the ulnar collateral ligament (UCL). An injury to this area may go by a few different names: gamekeeper's thumb, skier's thumb, and break-dancer's thumb. If you completely tear your UCL, you will need surgery to repair it.

Let's look more closely at a sprained thumb injury, though, and learn about the causes, symptoms, diagnosis, treatment options, and ways to avoid a sprained thumb injury.

A sprained thumb injury can involve either a partial or total rupture of your thumb's ulnar collateral ligament (UCL) at the metacarpophalangeal joint (MCP). It is a common injury and a painful one, accounting for 86% of all injuries involving the base of the thumb.

If untreated or misdiagnosed, this type of injury can cause long-term instability of the thumb, leading to chronic pain, weakness, and premature arthritis.

When you have a sprained thumb, it will be because of a torn UCL most of the time. The UCL is divided into two sections: the accessory collateral ligament (ACL) and the proper collateral ligament (PCL). These two parts work together to keep your thumb base stable. You also have a radial collateral ligament (RCL) on the opposite side of your thumb. It, too, can be injured, though much less frequently than your UCL.

When you fall on your thumb or jam it hard into a surface, that can cause a thumb sprain injury. This type of UCL injury is typically called a "skier's thumb." Your UCL ligament can also be injured slowly over time by repetitive grabbing and twisting movements of the thumb, an occurrence known as "gamekeeper's thumb."

You can tear your UCL in a variety of ways, though. It is detachable from the proximal phalanx. It is possible to pull it from the metacarpal bone, and you can also rip it down the middle. The most common location for an avulsion fracture is the distal attachment to the proximal phalangeal base. An avulsion fracture occurs when a tiny piece of the bone separates from the bone with the ligament.

Any force that bends your thumb far backward enough can tear your UCL. For example, if you fall while still holding onto your poles while skiing, the force of your hand slamming down onto your thumb may tear the tissue. Due to accidents like this, a sprained thumb is a common hand injury.

Your thumb and hand may bruise and swell. You may have difficulty gripping things. For instance, you may be unable to open doors or hold items in your hand like you usually would. If your UCL is torn completely, the end of the ligament can form a lump under your skin.

Unfortunately, you may have to wait until the swelling goes down before healthcare professionals can conduct a physical examination.

Stener lesion. A Stener lesion occurs when a UCL tear affects the adductor pollicis muscle. As a result of the interference between this muscle and the MCP joint, the healing process becomes more complicated. Surgical repair is often necessary for this type of injury. A Stener lesion is common, occurring with 64% to 87% of all complete thumb sprains.

Your healthcare provider will use a grading scale to determine your sprain's severity. The three different grades include:

  • Grade 1: a mild injury where the ligament is stretched but not torn
  • Grade 2: a moderate injury where the ligament is partially torn
  • Grade 3: a severe sprain where the ligament is completely torn (this requires a much longer recovery period and possibly surgery)

The majority of sprained thumbs are Grade 1 or 2. Even in less severe cases, though, an examination can sometimes be painful, and doctors may use local anesthesia to numb the area as they examine your injury.

After a physical exam, healthcare professionals may want to run more tests to learn more about your strain. Further imaging testing can include the following measures:

  • X-ray: An X-ray will take pictures of your bones to see if you have an avulsion fracture.
  • Stress X-ray: During a stress X-ray, your doctor will apply tension to the injury to determine the joint's stability. However, stress X-rays are becoming less common because of the risk of displacement. Displacement could cause a Stener lesion.
  • MRI: An MRI can help to diagnose a Stener lesion and provide other details that X-rays can't. An MRI can even help determine the level of the sprain and whether or not you will need surgery.
  • Ultrasound: An ultrasound can help your doctor determine if any partial tears or accumulated fluids surround the joint. An ultrasound can also help determine if there is a Stener lesion or a need for surgery.

Skier/gamekeeper's thumb treatment will differ depending on whether it is partial or complete and what grade your sprain is. 

For example, a Grade 1 strain will usually benefit from the P.R.I.C.E. treatment. The P.R.I.C.E. treatment includes:

  • Protection: Wearing a thumb splint to keep from reinjuring it.
  • Rest: Avoid using your hand for at least 48 hours after the injury.
  • Ice: Apply ice to the area. Ice will help to reduce swelling and pain.
  • Compression: Wrap up your thumb with a compression bandage
  • Elevation: Keep your hand elevated above your heart as often as possible.

In the case of a Grade 2 strain, your healthcare professional will most likely immobilize your thumb with a splint or a thumb spica cast. You can also apply ice. You may need to stretch the joint once it heals to regain a normal range of motion.

Surgery, meanwhile, is often necessary for:

  • Grade 3 ruptures
  • A Stener lesion
  • Displaced avulsion fractures
  • Large articular surface fractures
  • Long-term instability of the MCP joint

If you need to undergo surgery, your doctor may have you wear a short arm cast or a splint for 6 to 12 weeks after the procedure.

There are a few ways to prevent a sprained thumb. Some things that you can do include:

  • Stretch your hands and fingers daily.
  • Stretch your hands and fingers before participating in sports or physical activity.
  • Wear proper shoes when you play sports and make sure that they are tied correctly so you don't trip.
  • Wear gloves when you play sports.
  • If you are skiing, remember to let go of your poles if you fall.
  • Tape your fingers before you play sports.