Ringbone and Sidebone
Ringbone is the ossification (remodeling/laying down of excess bone) on the long and short pastern bones. Ringbone on the coffin joint (coffin bone+short pastern) is referred to as "low ringbone," while ringbone on the pastern joint (short pastern+high pastern) is called "high ringbone." Imbalance and unnatural forces on the joints cause the changes. Comfort level varies from horse to horse, with some being severely lame and others suffering only a loss of range of motion. It may or may not be seen/felt through the skin of the horse, depending on severity. On a radiograph it would show up like this:
And the bones themselves look like this:
Sidebone is the ossification of the lateral cartilages which are nestled again the palmar processes of the coffin bone in the back of the hoof. The lateral cartilages are where the bar corium exists. Heel contraction and other imbalances and extreme forces cause the ossification. There seems to be a trend of drafts and draft crosses developing it for reasons that are not clear yet (perhaps their large size and thus greater concussion??). Many horses are not bothered by the condition, but some are. It may or may not be seen/felt at or above the coronet band, depending on severity. On a radiograph it looks like this:
And the actual bone:
Photographs Copyright Cheryl Edwards-Henderson
Radiographs:
1, 2, 3, 4