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Condition

Swan Neck Deformity

A finger posture where the middle joint is hyperextended and the fingertip is bent down, usually from rheumatoid arthritis, chronic ligament stretch, or an old tendon injury.

What is swan neck deformity?

A swan neck deformity describes a characteristic finger posture: the middle joint of the finger (the PIP joint) bends backward into hyperextension, while the fingertip joint (the DIP joint) is pulled into flexion. The finger comes to resemble the curve of a swan's neck. It is not a disease on its own — it is a mechanical pattern that develops when the delicate balance of tendons and ligaments around the finger joints is disrupted.

Common symptoms

  • A finger that bends backward at the middle knuckle and down at the fingertip, especially when the hand is relaxed
  • Trouble making a full fist because the finger "catches" in the hyperextended position before it will bend
  • A clicking or snapping sensation as the finger is forced past the catch into a bent position
  • Aching, weakness, and difficulty grasping small objects
  • In mild cases, the deformity is cosmetic more than functional; in more advanced cases, the finger becomes rigidly stuck

Why does it happen?

A swan neck deformity develops when the structures that hold the PIP joint in its normal position give way. The most common causes are:

  • Rheumatoid arthritis. Chronic inflammation stretches the supporting structures on the palm side of the PIP joint (the volar plate), allowing the joint to hyperextend.
  • Untreated mallet finger. A chronic mallet finger can shift the balance of extension forces to the middle joint, which slowly hyperextends over time.
  • Chronic volar plate laxity. Injury or overstretch of the ligament on the palm side of the PIP joint, sometimes in patients with naturally loose joints.
  • Intrinsic tightness. After trauma, surgery, or a long period of immobilization, the small muscles inside the hand can scar in a way that pulls the middle joint into hyperextension.
  • Cerebral palsy or other spasticity disorders. Imbalanced muscle tone can produce the same deformity.

How it is diagnosed

Diagnosis is made on exam. Dr. Barrera will look at the resting posture of the finger, test whether the deformity is flexible (can still be corrected passively) or fixed, and examine the extensor tendon at the fingertip, the PIP joint, and the small muscles inside the hand. X-rays show the joint alignment and any arthritis.

A useful classification divides swan neck deformities into stages: (I) flexible in all positions, (II) flexible only with the MCP joint bent, (III) stiff PIP joint, and (IV) stiff PIP joint with visible arthritis. Each stage has a different treatment.

Treatment options

Non-surgical treatment

  • Silver ring splints or figure-of-eight splints. Small, low-profile splints worn on the finger during the day. They block PIP hyperextension but still allow full finger flexion, so the finger can work normally while the splint is on. For many patients with mild, flexible swan neck deformities this is the primary treatment.
  • Hand therapy. Stretching the tight intrinsic muscles and strengthening the flexors can improve mild deformities, particularly when the cause is intrinsic tightness rather than ligament damage.
  • Treating the underlying disease. In rheumatoid arthritis, good medical control of the disease is essential. If a mallet finger is the cause, that needs to be addressed on its own.

Surgical treatment

Surgery is considered when the deformity is interfering with function or is progressing despite good non-surgical care. The choice of operation depends on the stage.

  • Soft-tissue rebalancing. For flexible deformities, a small procedure tightens the palm-side ligament of the PIP joint using a strip of a local tendon (such as a slip of the flexor digitorum superficialis). This recreates a stable stop that prevents hyperextension.
  • Oblique retinacular ligament reconstruction. Another soft-tissue option, particularly when a mallet finger is driving the deformity, that rebalances extension forces between the PIP and DIP joints.
  • Intrinsic release. When tight small muscles inside the hand are pulling the PIP into hyperextension, releasing a portion of them corrects the imbalance.
  • PIP joint fusion or replacement. For stiff, arthritic PIP joints, the joint itself needs to be addressed — either fused in a functional position (very reliable, no motion) or replaced (motion preserved, but more complex).
  • Treatment of an underlying mallet finger. Sometimes correcting a long-standing mallet with a DIP fusion or a tendon-rebalancing procedure eliminates the driving force behind the swan neck.

What to expect at your visit

Dr. Barrera will examine the hand, determine which stage the deformity is in, and identify what is driving it. Many patients with mild deformities do very well with a small ring splint and hand therapy. Surgery is reserved for deformities that are progressing, that are catching and locking, or that are part of a broader rheumatoid reconstruction.

Dr. Barrera's approach

The key to treating a swan neck deformity is figuring out what is driving it. A swan neck from an untreated mallet finger needs a different operation than a swan neck from rheumatoid arthritis or from intrinsic tightness. A small, well-made ring splint is a surprisingly powerful tool for flexible deformities. Surgery is saved for cases where splinting and therapy are not enough, and the operation is tailored to the underlying cause.

When to call the office sooner

Call us if the finger becomes acutely locked and you cannot move it, if a finger suddenly loses the ability to straighten (which may indicate a tendon rupture, particularly in RA), or if you develop severe pain, warmth, and swelling in a single joint.

Related

Rheumatoid arthritis · Mallet finger · Boutonnière deformity

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