A distension of the tarsocrural (tibiotarsal) joint (the uppermost joint of the hock) which is characterised by three fluctuating swellings on the dorsomedial, medioplantar and lateroplantar aspects of the joint. This disease my be unassociated with lameness, heat or radiographic change. In such cases, the cause is simply an increased production of joint fluid due to low grade synovitis (inflammation of the membrane lining the joint pouch).