Figure 4.

Schematic of the Elson test used to identify injury to the central slip. (a) The patient places his or her hand over the edge of a surface with the digits flexed at the proximal interphalangeal (PIP) joint and hanging freely. The examiner applies firm, constant pressure to the digit in question at the level of the middle phalanx. The patient then attempts to extend the finger at the PIP joint in opposition to the examiner’s applied force. (b) If the patient is able to extend the PIP joint while the distal interphalangeal (DIP) joint remains pliable, it can be concluded that the central slip is intact. (c) If there is an injury to the central slip, the patient will only be able to extend the PIP joint through the use of the lateral bands, which will lead to DIP joint rigidity and concomitant extension or even hyperextension through the DIP joint.