It has been hypothesised that pain originating from the distal interphalangeal joint (DIP) in horses can be attenuated by analgesia of the distal interphalangeal (DIP) joint or navicular bursa (NB) and palmar digital (PD) nerve block. To test this hypothesis, 6 adult horses with lameless due to exostosis at the extensor process of the third phalanx were selected. Both synovial structures and PD nerve were blocked and the effects on the lameness were quantitatively scored. Lameness score was high at the trot before injection of lidocain HCl around the PD nerves and DIP joint, and significantly reduced 5 minutes after administration of drug around the PD nerves (P<0.05), and into the DIP joint (P<0.0001), at the walk the difference was even greater and became 0 after DIP joint analgesia. Lameness score was also high at the trot and walk before injection into the navicular bursa and no significant differences was seen 5 minutes after navicular bursa analgesia in both trot and walk (P>0.05). Fifteen minutes after navicular bursa analgesia, significant reduction of the lameness at the trot and walk was seen (P<0.05). It is concluded that, pain arising from the third phalanx such as extensor process exostosis should not be eliminated as a possible cause of lameness, when lameness is significantly reduced by diagnostic analgesia of any of related structures.

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