Swan neck deformity
- Occurs in about 50 per cent of rheumatoid arthritis (RA) cases, but may also occur as a congenital phenomenon or following trauma.
- Develops with hyperextension of the proximal interphalangeal (PIP) joint and flexion of the distal interphalangeal (DIP) joint.
- May affect one or more fingers but not the thumb.
- The deformity is initiated by a flexor synovitis that increases the flexor pull on the metacarpophalangeal joint.
- Extending the fingers causes stretching of the collateral ligaments at the PIP with hyperextension at this joint and reciprocal flexion at the DIP.
- Severe cases may suffer joint destruction and contractures.
- Causes considerable disability.
- Tests that confirm the diagnosis of RA include: rheumatoid factor, which is positive in 80 per cent of cases; analysis of synovial fluid to distinguish from non-inflammatory and infectious arthritis; ESR and X-ray.
- Surgery should be considered when the patient cannot actively flex the PIP joint.
- Early referral for assessment is important.
- May develop in cases of progressive arthritis or following trauma.
- Occurs in about half of patients with RA.
- Presents with flexion of the PIP and hyperextension of the DIP.
- May affect one or more fingers, including the thumb.
- In RA, follows chronic synovitis in which the PIP joint is forced into flexion which increases tension on the DIP extensors.
- Following trauma, the finger is semi-flexed and movement of the joints decreased.
- May not develop for two to three weeks following injury.
- In RA, symptoms may be mild, moderate or severe, when the PIP joint can no longer be passively extended.
- Check for history of recent injury.
- Tests as for swan neck deformity will help in the diagnosis of RA.
- Initial treatment with splinting may be helpful after trauma or in RA when symptoms are mild.
- In RA, moderate and severe cases may be helped by surgery. However, surgical reconstruction of the joint and/or complications can reduce function.