Injuries to the central slip of the extensor tendon of the hand can easily be missed until the Boutonniere Deformity sets in, with its associated functional limitations. The Elson test is a diagnostic test used for early detection of injuries to the central slip of the extensor tendon. 
- Have the patient rest their hand on a table, with the PIP joint of the involved finger flexed to 90 degrees over the edge of the table.
- Palpate the middle phalanx of the involved finger, then ask the patient to extend the PIP while providing some resistance.
- Test is POSITIVE if the patient has a weak extension at the PIP joint with (hyper)extension at the DIP.
- Test is NEGATIVE if the patient has strong extension at the PIP joint, while the DIP remains floppy.
A cadaveric analysis of four non-invasive tests for central slip integrity found that Elson's Test was the only one to accurately discern central slip integrity in simulated injuries.
- Elson RA. Rupture of the central slip of the extensor hood of the finger. A test for early diagnosis. J Bone Joint Surg Br. 1986 Mar;68(2):229-31. doi: 10.1302/0301-620X.68B2.3958008. PMID: 3958008.
- Rubin J, Bozentka DJ, Bora FW. Diagnosis of closed central slip injuries. A cadaveric analysis of non-invasive tests. J Hand Surg Br. 1996 Oct;21(5):614-6.
- Physical Therapy Nation. Central Slip Rupture Test. Available from: https://www.youtube.com/watch?v=M3U5MSb2Piw [last accessed 30/11/2020]