A side issue

Sidebone itself rarely causes lameness, but it can lead to conditions that do. Thijs de Bont MRCVS explains why, and measures to help avoid such problems

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SIDEBONE is a condition in horses whereby the usually soft lateral cartilages of the foot harden through a process known as ossification.

The lateral cartilages - also known as the ungular or lateral collateral cartilages - are flexible, curved structures that extend from either side of the distal phalanx (coffin bone) towards the bulbs of the heels. They have a C- to L-shaped configuration and vary in thickness along their length and between horses.

The lateral cartilages function as shock absorbers by distributing load through the foot during weight bearing, by providing flexible support and allowing for the heel region to expand under load.

The process of ossification appears to occur due to repetitive loading and concussive forces. Poor hoof conformation, in particular lateral to medial (outer side of the hoof to the inner) foot imbalance resulting in uneven distribution of load, is a contributing factor.

Older horses are more commonly affected, with draught and native coldblooded breeds predisposed. The condition appears to be heritable in Finnish Trotters, with up to 80% of individuals of that breed affected.