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Steroid injection for stenosing tenosynovitis of the extensor carpi ulnaris

joint may be caused by pathology at the level of the PIP joint. On occasions, with hyperextension of the PIP joint, the lateral bands of the extensor tendon mechanism sublux dorsally, snapping palmarwards during flexion or locking the joint in hyperextension. Proximal interphalangeal joint triggering or locking in flexion may also be caused by prevention of lateral band migration dorsally. This has been described with catching of the lateral band of the extensor tendon palmar to a chondroma (Yamauchi et al., 2008), triggering of the lateral band of the extensor tendon on a Bouchard’s node (Durand et al., 2011), or in cases with distended fibres between central and lateral bands due to rheumatoid arthritis (Stellbrink, 1971). Posttraumatic subluxation of the extensor lateral band due to retinacular ligament injury at the level of the PIP joint has also been described (Ikeda et al., 2000). Our case was caused by catching of the radial collateral ligament on the palmar side of an exostosis, causing locking of the PIP joint in flexion and requiring passive reduction. In this case, the extensor mechanism was free of any lesion. Excision of the exostosis and reinsertion of the origin of the radial collateral ligament cured the problem.