Your thumb has two bones called the phalanges. The most common fracture associated with a broken thumb is actually to the larger bone of your hand known as the first metacarpal. This bone connects to your thumb bones.

The first metacarpal starts at the webbing between your thumb and index finger and extends back to the carpal bones of your wrist.

The place where the first metacarpal joins your wrist is called the carpo-metacarpal (CMC) joint. Most thumb bone fractures occur at the base of the first metacarpal, just above the CMC joint.

If you suspect that you have a broken thumb, you should seek immediate medical help.

Symptoms of a broken thumb include:

  • swelling around the base of your thumb
  • severe pain
  • limited or no ability to move your thumb
  • extreme tenderness
  • misshapen appearance
  • cold or numb feeling

Many of these symptoms can also occur with a severe sprain or ligament tear. You should see your doctor so they can determine the cause of your injury.

A broken thumb is usually caused by direct stress. Common causes may include a fall on an outstretched hand or an attempt to catch a ball.

Bone disease and calcium deficiency both increase your risk of a broken thumb.

A broken thumb can result from extreme activity or an accident. Your thumb can also break from twisting or muscle contraction. Sports where a broken thumb is more likely to occur include:

  • football
  • baseball
  • basketball
  • volleyball
  • wrestling
  • hockey
  • skiing

Wearing the proper protective gear, such as gloves, padding, or taping, can help prevent thumb injuries in many sports.

Learn more about treating and preventing sports injuries.

You should see a doctor immediately if you suspect you have a broken or sprained thumb. Both types of injuries may require immobilization with a splint and surgery. Waiting for treatment can lead to complications or slow down your recovery process.

Your doctor will examine your thumb and test the range of motion at each of your joints. They’ll bend your thumb joints in different directions to determine if you’ve injured your ligaments.

An X-ray will help your doctor detect a fracture and determine where and what type of break you have.

Immediate first aid

If you suspect you’ve fractured your thumb, you can apply ice or cold water to the area to reduce swelling. Immobilization of your hand with a splint can help if you know someone with the proper knowledge to do so.

Learn how to make a splint.

Keep your injured hand elevated above your heart. This helps to reduce swelling and bleeding, if any.

Don’t rely on these measures alone. If you suspect a fracture or sprain, these methods may help while you’re waiting for immediate medical attention.

Nonsurgical treatment

If your broken bone fragments have not moved too far out of place, or if your fracture is in the middle of the bone shaft, your doctor may be able to set the bones without surgery. This is called closed reduction. It can be painful, so sedation or anesthesia may be used.

You’ll be set in a special cast, known as a spica cast, for six weeks. This cast holds your thumb in place while your bone heals. The spica cast immobilizes your thumb by wrapping around your forearm and thumb.

Surgical treatments

If there’s been a lot of displacement of your bone fragments, or if your fracture reaches the CMC joint, you’ll likely need surgery to reset the bone. This is called open reduction. A surgeon specializing in hand surgery will probably be performing your procedure.

In about one third of breaks to the first metacarpal, there’s only a single broken fragment at the base of the bone. This is called a Bennett fracture. The surgeon inserts screws or wires through your skin to hold the broken pieces in proper position while the bone heals.

In a break called a Rolando fracture, there are multiple cracks to the large bone at the base of your thumb. During surgery, a specialist will insert a small plate and screws to hold your bone fragments together while your bone heals. This is called an open reduction with internal fixation.

In some cases, your surgeon will extend the plate device outside your skin. This is called external fixation.

If you’re set in a spica cast, you’ll need to wear it for six weeks. Sometimes children don’t need to wear it that long, so be sure to follow your doctor’s instructions.

If you have surgery, you’ll wear a cast or splint for two to six weeks. At that point, any pins that were inserted will be removed. Physical therapy is usually prescribed to help you regain movement of your thumb.

Depending on the severity of your injury, it may take three months or longer to recover full use of your hand.

Arthritis is a common complication of a broken thumb. Some cartilage is always damaged by the injury and isn’t replaceable. This increases the chance of arthritis developing in the injured thumb joint.

A study of people who received nonsurgical treatment for Bennett fractures found a high incidence of joint degeneration and range-of-motion problems after 26 years. This led to greater use of surgery for Bennett fractures. There’s no current long-term study of the outlook for people who’ve had surgery for Bennett fractures.

A broken thumb is a serious injury and requires immediate medical attention. As long as you seek proper and quick treatment, your chances of recovery and full use of your thumb are very good.