Horses commonly develop a range of hoof distortion, due to a number of causes. Diet and environment are huge factors, which can damage laminae connections, allow hooves to overgrow, increase susceptibility to infections... fail to provide what is needed to develop a strong, functional hoof in the first place. Mechanical factors, such as too much pressure being placed on the walls and too little support under the foot can lead to 'distal descent' as the internal structures 'sink' within the capsule and the sole thins. Leverage forces on long walls, particularly at the toe cause stretching and separation of the laminae from the ground surface and resulting flares, cracks and infection.
Ground parallel or lower angles of the back of P3 cause a 'broken back' pastern angle, putting a lot of stress on both the extensor process(top/front of pedal bone) region and the navicular region. Alternately, high heels cause 'rotation' of P3 the other way, with the toe pointing into the ground.
A horse may have 'clubby' feet for a variety of reasons. One reason is failure of development of the back of the foot, which causes him to be uncomfortable impacting on his heels. Landing toe first naturally wears the toes shorter and allows heels to grow high.
Combined with breakdown of lamellar connection due to laminitis &/or failure to manage the toes from flaring with the added pressure, the hoof walls can separate completely. The sole can be flat or even bulging at the tip of P3. In severe cases P3 can even penetrate the sole and in chronic cases the tip of P3 is lost or 'remodelled'.
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