What Is Swan Neck Deformity?

Swan neck deformity is an abnormal positioning of the joints in your fingers. It’s named because of the way an affected finger bends, giving it a curved appearance similar to the neck of a swan.

The deformity can be caused by trauma or injury to the finger, as well as by diseases that attack the joints of the fingers, such as rheumatoid arthritis (RA).

Swan neck deformity can be treated with surgical and nonsurgical options. This overview will cover how the deformity develops, who is most likely to develop it, and how it can be treated.

Causes

Swan neck deformity develops when one of the tendons or ligaments that control the movement in the fingers is injured or damaged. Any condition that tightens or limits the movement of the fingers by damaging the tiny fibers in the fingers that allow them to move can lead to the deformity.

The deformity can happen from a single injury or a combination of injuries, including:

• If the thick ligament that connects the bones in your fingers (volar plate) becomes weak or tears. Volar plate injuries can occur when a finger is jammed (also known as a sprain).
• If the tendon that flexes the middle finger joint (flexor digitorum superficialis) is torn or damaged. A common name for this injury is jersey finger.
• If the tendon that straightens the end joint of your finger (extensor digitorum communis) is injured. This injury is sometimes called mallet finger or baseball finger.
  

Many factors can contribute to these injuries. Examples are sports injuries and trauma to the fingers. There are also diseases and conditions that can damage the fingers, including:

• Rheumatoid arthritis
• Psoriatic arthritis
• Cerebral palsy
• Ehlers-Danlos syndrome
• Parkinson’s disease
• Stroke
• Nerve disorders

You can reduce your risk of encountering some of these causes—for example, by protecting your hands from injury while playing sports. However, you cannot necessarily avoid health conditions like Ehlers-Danlos and Parkinson’s disease.

That said, there are treatments that might help prevent swan neck deformity even if you have an inherited health condition that makes it more likely that you will develop it. The first step is to talk to your doctor about any risk factors that you have, such as:

• A history of injuries to the fingers or hand
• Connective tissue disorders
• Joint diseases like arthritis
• Nerve damage

Your age and sex do not affect your risk of developing swan neck deformity. However, research has shown that women with RA develop swan neck deformity more often than men with the condition do.

Symptoms

The deformed appearance of the affected finger is the primary sign of swan neck deformity. The characteristics of the deformity include:

• The first section of the finger—from the knuckle/metacarpophalangeal (MCP) joint to the first joint/proximal interphalangeal (PIP) joint—is straight or bends downward.
• The second section—from the first/PIP joint to the second/distal interphalangeal (DIP) joint—is hyperextended and points up from the hand.
• The third section—from the second/DIP joint to the fingertip—has joint flexion and turns inward toward the hand.

Aside from its appearance, swan neck deformity can also cause other signs and symptoms in the affected finger, including:

• Locking of the joint
• A snapping sound when you bend your finger
• Pain
• Stiffness
  

Diagnosis

Your doctor might be able to diagnose a swan neck deformity just by looking at your finger. They will also ask you about your personal and family medical history, and about any traumatic injuries that you may have had involving the affected hand.

Imaging studies can give your doctor a clear view of what the injury looks like inside your finger. An X-ray is usually enough, but your doctor might need more than one picture to see your finger from several angles.

Staging

Once a diagnosis of swan neck deformity has been made, the next step is to grade the severity of the condition to determine the best treatment.

The Nalebuff classification of swan neck deformity is the most commonly used classification system for grading deformities of the fingers. It is mainly used for deformities that are caused by arthritis. The system takes into account the severity of deformities, as well as how the deformities impact the function of the surrounding hand.

According to this system, deformities are classified from type 1 to 4:

• Type 1: The middle joint of the finger (PIP joint) is flexible in all positions of the knuckle (MCP joint).
• Type 2: The middle joint of the finger (PIP joint) is flexible in only certain positions of the knuckle (MCP joint).
• Type 3: The movement of the middle joint of the finger (PIP joint) is limited regardless of the position of the knuckle (MCP joint).
• Type 4: The middle joint of the finger (PIP joint) is stiff and appears damaged on an X-ray.

Treatment Options

Depending on the stage of deformity, your doctor might recommend either surgical or nonsurgical treatment. Deformities that are in the early stages can often be treated with splinting or physical therapy, while more severe grades of deformity might require surgery.

Surgical 

Surgical treatments are usually reserved for the most serious levels of deformity, or to prevent further damage. Surgery may also be performed when the middle joint of the finger can no longer bend or it makes a snapping sound when it’s bent.

People who choose not to wear external splints that are often used as a nonsurgical fix might be candidates for surgery.

The surgical options for swan neck deformity include:

• Rebuilding the volar plate
• Ligament reconstruction
• Internal splinting
• Total joint reconstruction or replacement

Nonsurgical

The primary nonsurgical option for treating swan neck deformity is the use of an external splint. A silver ring splint or another splint that supports the joints without limiting the function of your hand is usually used.

Progressive casting is another option. This treatment involves casting the finger at different stages to restore its natural positioning.

Physical therapy can be used alongside splinting or casting to help restore strength and mobility to damaged joints.

Nonsurgical strategies are usually reserved for early or mild deformities. They might not be an option in more severe cases where the movement of the joint is already limited.

Summary

Swan neck deformity is a common complication of rheumatoid arthritis, but it can also develop after finger injuries or as a result of conditions that affect your ligaments, tendons, or connective tissues.

Mild cases of swan neck deformity can usually be treated with nonsurgical techniques like splinting, but more severe cases could require surgery.

A Word from Verywell

Many conditions can cause painful damage to the joints. In some of these diseases, such as RA, the joints can be left disfigured as the disease progresses. Swan neck deformity is one type of disfigurement that can occur.

If you notice stiffness or a snapping sound in your finger, or it becomes hard to move, it’s important to tell your doctor. They can diagnose the deformity and determine the best way to treat it.